when pulling a loop
 

when pulling a loop should I drop prop pitch to ease the labour on the engine?

Not if you want to complete the loop....... Seriously though, you need all the power you can get on the upside, cutting back the Rpms is just going to cost you power when you need it most. Once you've cleared the top and gotten some speed back, you'll want to cut back on the power. You probably will want to open your radiator/cowl flaps as you will be going slow and producing a lot of power on the upside (of the loop) which is a perfect combination for making heat.