Installing 3/4" T&G subfloor over 11-7/8" engineered wood I-joists and not sure how skinny the last row of subfloor can be. If I make no adjustments I'll have a last row of subfloor that is only 10" wide. While that row will sit on I-joists that are 16" on center with one 2x6 squash block at each joist, not sure that's wide enough. Can adjust at center beam to make it closer to 2 feet wide, but a lot more work and will waste material. Any thoughts?

I don't know that I'd take that as Gospel. I'm not sure what the squash blocks will do for you: it seems to me that the major problem is the narrow subfloor board. I guess the SB's give the joists some more width to nail to.

What are you putting over the subfloor? If it's hardwood or something with an underlayment (e.g. sheet flooring), it seems to me that it would be OK but YMMV. If it's just carpet, I think I'd bite the bullet and make it two joists wide.

The skinny row (10") of subflooring is actually going to run perpendicular to the joists. Regardless, I think you're right and I'll do the extra to play it safe, as there's nothing but carpet going on top. Thanks for your input.