All the above are good responses.
I have a Venus, built stock, with an OS .46FX, and it will do very tight loops. Here are a couple of tips to help stop your snap problem.
1. Be sure and take the time to balance the model and set the control throws as in the instructions, before experimenting with any changes.... Always a good way to start.
2. The way to fly "safe" is to set your highest rate so that it's just below the threshold of the snap, at the speed you usually loop at. An easy way to check this is to watch your loops as you fly them. If the loop is smooth, great. If it's "jerky", more like an octagon than a loop, that tells you that you're right on the edge of a stall/snap.
3. Aerobatic planes are made to snap easily, for crisp entry into maneuvers that require it, such as a spin. Trainers are usually built so that the wing will (more softly) stall and recover before the stall can intensify.
Once you get the Venus trimmed, it's a lot of fun to fly, especially in knife edge. Here's an example trim chart that may help.
http://www.nsrca.org/trimA.htm