TM velocity reducers are an option, however they allegedly are not very effective when firing in full auto, as well as some places won't even allow you to play with them (guessing due to the assumption of a hot gun). If you're at a private field and it's close-quarters and your entire team plays in semi-auto only, then a TM-VR might not be a bad idea.
If you're comfortable working on your mechbox, swap the spring out for one designated to shoot lower. If you're not comfortable, fish around your friends who are into the sport and see if they are, pitch them a few bucks for the labour, and you're set. If not, try and find a gun doc in the area. Not that switching the spring is probably most cost effective, and not as high maintenance. Don't know how reliable the TM VR is in terms of reliability, but judging by how it works it probably would need a part replacement more often than not.
Primary: Custom WE M16A3
Secondary: KWA MP9
Side: Custom WE M1911A1