I tend to agree with scott and would dispense with the screen, at least until you learn your oven better. The screen will just space your pie from the heat of the stone and prevent the bottom from browning sooner. I recall that at least one of our members has previously used both a screen and stone in a convection oven, so it is at least theoretically possible to do, although I don't recall the particular details where both the screen and stone were used.
I don't have much personal experience with convection ovens but I understand that they cook faster and often at higher oven temperatures than non-convection ovens. To succeed with making pizzas in your particular oven, it will help to master the oven's thermodynamics. The pizza will also have its own thermodynamics characteristics by virtue of its size, dough thickness, and the types and amounts of sauce, cheeses and toppings used. The oven's thermodynamics and the pizza's thermodynamics will have to be compatible to get optimum results.
In your case, you might want to try placing another stone above the one you are now using to serve as a barrier between your top heat source and the pizza. To test out the concept, you might try using inexpensive unglazed quarry tiles instead of the second stone before deciding to buy the second stone. You may also want to try a lower oven temperature and a longer bake time to see if that will help balance out the top and bottom bake. You most likely will also have to do some experimenting with the two oven rack positions you decide to use. If you decide to use two stones or stone/tile combination, you will need to allow for a longer preheat time to get the stones/tiles up to temperature.
My recollection is that some of our members, including Lydia, use convection ovens, and hopefully they can offer some guidance that may help you with your particular brand and design of convection oven.