I recently ditched the 44t and fitted a 36th middle on a 3×9.
Not an slx crank though,.
It works fine – I can use the whole cassette with the 36t and actually use the 22t a lot less than I thought I would.
However, the FD is quite fiddly to get exactly right. Limit screws and FD height had to be precise. Even now I get a tiny bit of chain rub on the FD cage when in 36×11, but I can live with it. I also drop the chain from time to time but I think I left it one link too long.
It looks ok (i ended up with red alloy chainring bolts as they were the cheapest short ones) the FD looks too high, as there’s no big ring, but it’s not so bad that I need to buy an m665 FD.
Edit: forgot to mention that 2×9 is in fact awesome, but typing on a phone is not.