Hoping some of those more experienced than I can help with some layout options before I get started. My wife picked out some very nice pre-finished 5" wide hickory flooring that we plan to put throughout most of our first floor (1000sqft). I researched the product and company and it seems to be a quality product. I realize that hickory tends to expand/contract more than other woods, and I live in MN where we have dry winters and humid summers. I have a humidifier for winter and run the AC in the summer, but I'm sure I'll still see some movement. The flooring has been cross stacked in the house for 2 weeks and will stay there for another 2wks. I've been trying to measure moisture content, but I cant find a meter that works - I just get 0% all the time.

The space I will be working in is essentially a big L shape. The flooring will run about 40ft in length, and about 35ft in width. My concern is with the width and the amount of movement I'll see. There are links below to 3 possible layouts (couldnt figure out how to attach or embed....).

Option 1 - I could start at my left wall and work my way all the way to the right. This is fairly straight forward, but it will maximize the movement seen at the walls.
https://flic.kr/p/2ifSB4k

Option 2 - Start in the middle with a spline and work both left and right. This would aim to split the expansion/contraction to two different directions. I understand that wood grows towards the tongue more than the groove.
https://flic.kr/p/2ifSB4A

Option 3 - The most complicated option. I would start at "middle" of the left half and the middle of the right half with two splines working my way out from both. Where the two sections meet in the middle at the doorway, I would put some form of a T molding to cover up a planned expansion joint.
https://flic.kr/p/2ifP8ro

Am I overthinking this? It's about 30-35%RH in the house right now with the humidifier on (any higher and the windows get condensation) and I suspect it will be in the 50s this summer.

Thanks for any help!

Seems like you checked all the boxes and your head is in the right place to anticipate and reduce problems down the line. That's good!

If you are getting 0% on a digital meter, its likely between 1-5% Moisture content, and the meter doesn't display lower than 5%. My General Tools meter from amazon works like this and it is explained in the accompanying instruction manual. A more expensive meter with an analog gauge like a Wagner will give you % between 0-5% if needed, but chances are your material is acclimated enough. If its 35%RH in the house now, and you can keep the RH at or below 55% in the summer, then you will be in good shape. Make sure you leave 3/4inch or so at all vertical obstructions (including at those cabinets) and you should be fine.

If my guys were installing, they'd go with option 1. I don't like to back fill with a slip tongue if I don't have to.

Thanks for that input. With option 1 installed in the dry season, will it expand in the summer and then leave big gaps the next winter? Or will it continually expand and "squeeze" the planks in the summer and then relax to neutral in the winter?

Out of curiosity, why the aversion to the use of splines?

I prefer #2 with a spline. The only detriment to using a spline is you will need to use some top nails to hold the boards when you start. If you use glue for the starter board and can nail from the back side of the board with a cleat, or finish nail that is not in the way of the spline, you will not need top nails. You will not need an expansion gap at the doorway. 5 inch wide board will take you through the doorway to start the other room.When using aquabar paper, the first row is installed before the paper is put down. I use sub-floor adhesive on the first rows and the last row.
I like to lay the flooring parallel to the sink cabinet, which has the possible moisture problem if you have a dishwasher. When the boards point toward the appliance and you have a problem, it will be much greater because moisture will be drawn away with capillary action. When the boards are parallel to the sink cabinet you will notice slight cupping along the first few rows, instead of the ends of a bunch of rows.

Since I do a lot of warranty work/new construction I tend to follow the install instructions to the letter whenever possible. Anytime you need to modify the installation method by changing fasteners (like using glue for the starter board as Pete suggests - I'd never face nail in a doorway) you run the risk of a claim being rejected down the line, so I just play it safe and avoid it. Moreover, option 1 takes less time and most crews are piecework, which is why my installers would go with that route

That said - since you have the time and patience option 2 will likely give you more piece of mind in the long run.

Pete, good input on the dishwasher stuff. My neighborhood has had a lot of DW leaks and I'll be checking mine when it's out. Not sure why they dont make a leak tray for them like they do water heaters...

My pictures were a little vague - the black box in the cabinets is the oven. The sink and DW are actually on the left side which would be parallel to the DW cabinets.

Do you use both Aquabar AND felt paper under your flooring? I have a finished and dry basement below so I'm trying to decide what I'll put down.

Both can be used, but I like the waxed paper aqua bar. The advantage of tar paper is that it can be a little sticky which helps if your flooring is a little too dry. You can leave minor gaps between the boards that will fill in during seasonal variation of the humidity. It’s hard to make tiny gaps henthe flooring gets slammed in but the fastening gun. You can check what the final dimension will be according to the humidity w hen starting with a known moisture content. at times Ihave used flat washers between rows every 24 inches which hav come together after a couple of weeks or so.