The 33%/35% are pretty good at doing all the tricks the 40% can do .
The only catch -for precision flying -is the time/size frame.

Let's say you have a combination of 3/4 roll and 3/4 snap -then an up line then pull/push to another maneuver.
Unless you do this all in a tight sequence - the model gets out there pretty fast.
Now the size gets to be an issue -it is harder to see it (judges in particular.)
A really light well powered model can be flown more slowly and with the right skill level - held in and look good.
But the old bugaboo size difference give the advantage to the bigger model -
more time and a larger playing field .
IF the maneuvers for -say Sportsman, Advanced or Intermediate , were designed around using a 33% model -flown in a more restricted airspace (remember the box?), the advantage of the 40% would be nullified.
Or to go to the extreme -held in a tighter box -a really large model would be at a disadvantage.
There are easy ways to control model size.
As long as model size is unlimited and airspace is unlimited the bigger model always has the edge.
If this were not so -why would the winners in Unlimited all fly about 40% or larger ?
So
Leave model size up to the flyer -all classes .
Simply reduce the box size for for lower classes AND design the maneuvers to "fit well" in this box.