In your opinion would you obtain a faster speed with retracts or without, given the weight/aerodynamics tradeoff?

Weight has little effect on speed. More weight may take longer to get up to speed but to IDENTICAL planes other than weight, one weighing, say 2 lbs more than the other will theoretically reach the same top speed but the lighter one will get to that speed sooner (better accelleration). Now the drag caused by thick airfoils and landing gear have a larger effect on top speed. All aircraft have a drag coeffecient. A more streamlined ship will go faster than the one shaped like a brick wall. Then the next effect you can make on speed is prop sellection. In general a small diameter prop with a larger pitch will go faster so long as you are still reaching close to optimal RPM out of the engine. For example with an OS .46 AX if you want pulling power without to much speed an 11x5 or 11x6 prop would be near ideal now if you want to go fast with the same engine you might select a 10x8 or a 9x9 speed prop.