have any of you built a LAW replica gas powered airsoft rocket launcher? there are many instructional videos online but if anyone in the area has one let me know! I'm having issues with the how to make the compression chamber in a single tube rather than 2 tubes and 2 elbows. also, what size pipes did you use for the outer/inner chamber? because it should be retractable I need pvc pipes that fit together relativly tight. If you have any experience please let me know!