While removing an old—1827—hemlock random-width plank finished floor in a bedroom during a major renovation, most of the boards had been so heavily damaged during previous renovations as well as during my removal that they were beyond being used again. During my renovation, I installed a 3/4” OSB subfloor and thought I would cover it with new top-nailed random width hemlock planks (6” to 10” wide) as an homage to the material used by the original builders.

I’m aware that hemlock is a relatively soft wood, so I wouldn’t use it on a high traffic floor, but my impression is that it will be just fine in a bedroom.

My wife did an Internet search on hemlock flooring and saw several complaints that that material cups readily when used in wide planks and also splinters readily under foot. I’m thinking three Tremont brand antique-style black-oxidized square cut top nails on a 10” wide plank on 16” centers would be enough to prevent cupping and a coat of sealer covered by two or three coats of oil-based polyurethane ought to prevent splinters...but my wife is still a bit concerned about the negative things she read about hemlock on other Internet sites.

What do the folks on this forum—ideally the ones with some wide plank hemlock experience—think about my optimism and/or my wife’s skepticism about the use of this material in a bedroom?

What I see that is common with a fir floor, which is harder than hemlock, is damage from the bed posts because the flooring will not stand up to the concentrated weight
of the bed and people using it. It may be from jumping on the bed near a corner.
Maybe the cupping is the result of using wood that is not kiln dried to under 12% moisture content. I think it comes from the mill around 19%, usually. If you have time for it to acclimate to your home conditions, as per measuring the moisture content of the old wood, then matching the MC of the new wood to the old wood, you will be fine.
I think that tacking the new acclimated wood in place several rows at a time until you fill the whole room all the way across before you start to use the cut nails will help your floor stay put. I would pre-drill for the cut nails and install the nails so that the nail takes up the most space across the grain. If there are any gaps between boards, the nails will split the edge of the board so it presses against its neighbor so the boards will be even tighter together after all the cut nails are installed. Any cracks can be filled with pine colored wood patch by Zar pressed in with a narrow flexible putty knife and never crack and fall out. You will need to hand sand the filler after it dries so keep it neat. Nail near the edge so any gaps will tighten up as you nail and press the edges of the boards tight. With the boards tight there will be a minimum of splintering on the edges. It will not look pretty until the stain and finish is applied. Colored putty after the first coat of finish has been applied is another option instead of the latex wood patch, but the latex wood patch made smooth after it has dried will look the best and take the stain like bare wood.
Before cut nailing I would use finish nails to hold the rows together as you lay the floor across the room, filling the room with flooring. You could use sub-floor adhesive to assist in this process. After all the room is covered, but before you start installing the cut nails, would b e a time to sand the floor to remove the mill marks, finishing with 80 or 100 grit before staining a light warm brown color you can get by thinning walnut stain with neutral oil, or natural colored stain. The cut nails hammered almost flush with the surface after you pre-drilled holes through the hemlock will be great decor. Finish with clear coats. Have fun! It's a lot of work to have the old floor look that will hold up for another century or so.