Patrick, If you are not already commited to a design, do a search at www.thebeachcats.com There is a lot of info on the subject, and some great boxes/tubes. I purchased the large glass box from Hobie, and found it more time consuming, and way more expensive than building a plywood box from scratch. The boat I have now came with a nicely built wooden box. Only troubles were it was on the trailer backwards, and too high to get the boat on and off without lifting! I hacked it up a lot modifying it,but now it works great. Tad, after rebuilding the trailer for my first 17, it seems like more work to dunk than not to dunk. I'm with John on that one. Love my Cat Trax!