does anyone have any ideas of any straight edges that could be used when starting the initial row? maybe some sort of metal edge that could be screw down. i have used plywood and some other things, but wondered if anyone knows of any factory straight edges that are at least 8 ft. long. thanks for any suggestions

I use u channel aluminum the 1 inch by 3/4 inch. Get it in8 foot lengths and cut to varying lengths and drill holes in the middle of the track for screws.

I find it good for starting and for checking how flat the floor is.

I also use a 2x6" 8 foot channel of alluminum, I had for an old homemade motorcycle trailer I built years ago.

Works good for gluedowns, while kneeling on it, also.