For traditional full ups: main keep your right hand (twisting arm) in an L-shape/right angle throughout the drive up phase to ensure that the twist happens at the very top. Don't forget about the left arm -- make sure you use it drive the stunt up and then focus on whipping your right hand quickly when you get to the top to join it back to your left as soon as you can. Really focus on the feet and grabbing the heel quickly. Have the flyer's ball of foot in the palm of your hand - don't hold too far up under the arch or you'll lose the leverage for the spin.
Make sure secondary base and back are taking the toss up all the way to the top and keeping their hands up. Flyer should let main control the spin; she shouldn't spin herself. If they are getting their arms caught, that implies they are twisting before the top - so ensure the flyer isn't spinning herself early, main is waiting for the top (think of it like a show with a spin on top, not up and twist all in one motion) and side base and back are completing the toss.
Provided they spin at the top, arms should be out of the fray for the catch and won't get twisted :)
