Yes,
Two mosfets ( at least the FQA11N90) on one driver at 40 meters will give trouble.
(as shown by the scope pictures earlier)
for 160m and 75m , one driver per pair of fets is dandy.
But we know that already. It has been said quite often that one driver ( IXDD414) for each FQA11N90 is needed for 40m.
I was actually supprised at how well this one played by simply changing the low-pass filter from a 5mhz cut-off to a 9mhz cut-off.
'Digital' drive, from a square-wave source ( an Si570 based vfo )
Funny though, at 12volts, I am only able to get about 18-20 watts output and about 75+ watts with 24 volts.
This week sometime I plan on converting this rig to 4 mosfets/4 drivers.
Then see how it plays. I expect that the results will be different.

First though, I may use up some type 61 ferrite, and see how things go on 75 and 40m with those cores.. and THEN make the step to 4 devices.