My girls are 8 (level 5) and 11 (Level 8). They practice gymnastics 15 hrs/wk. This year, I agreed to let them do competition plus in-town cheer, for our town. This was only because their USAG seasons do not compete until January 09 and town/comp cheering will be done by Dec 7th.
Shortly after we signed up for cheer, our gym's All Star team kind of "disappeared" except for 3 girls. So the owner looked to the gymnasts to try to rebuild the team. He ended up getting 4 girls from the competitive gymnasts (my DD's and 2 others, a level 4 and a level 8). All summer, they practiced gymnastics from 5 to 8 pm and then cheering from 8 to 9pm two out of the 4 days. Now that school has started, they are practicing from 12 to 2 on Saturdays only, because we parents said that we cannot keep kids out that late on school nights. Because it is a rebuilding year, we are not being charged for the extra gym hrs needed for cheering. So far we've only had to buy sneakers. We will fundraise for uniforms. The competitions will be scheduled as not to interfere with gymnastics meets. So, for us, this has been working out.