John, what you describe is what I do with my IMAC planes.
I move the stick to mid throttle then adjust the curve to give me the speed I want. I then fly a 45 up, move the stick to 3/4 then adjust. Fly 45 down, move the stick to 1/4 then adjust. It works good.

I also have a memory set to allow for fun flying.
In this memory, I use the throttle setting described in the previous post.
In the air, I find that the speeds remain linear.
Don't know why this works for me and not you but it does.
Maybe because I never fly WOT at straight and level but on an incline or vertical.
You can also use the above setup as a start and then adjust it in the air to make it perfect.