The mold needs draft and draw, the angles of the part must allow it to release. I have the equipment to bag parts, it is not always necessary, the thing it does do is remove the excess resin and thus reduce the weight without reducing strength. Another factor on composites, 100% of the load/stresses goes through the stiffest fiber (carbon) until it fails, then it transfers the load to the glass if you are using a multi fiber composite structure..... The grain direction of a unidirectional is critical, 4* off of the direction of the grain can lose up to 99% of the stiffness in that direction . Tim