I'm new to using a crossbow and just bought a Wicked Ridge Invader X4. It was supposed to come with 3 aluminum bolts, but it didn't. Thought I would their length. The manual recommends 20 and 22 inch bolts. Is this just based on preference. 20's I imagine are lighter and quicker? 22's a bit heavier but better penetration? Going to buy some carbon ones tomorrow. Also, are mechanical broadheads different for crossbows, or any broadhead will work?