i dont have any un underside? the tent just is bolted to top bars of rack. the mounts that hold the rack/ pipe is electrical kendorf that you can buy from homedepot or lowes, it is made to hold electrical conduit pipe horizontally on ceilings, heavy duty and cheap, then just have poles bent, the poles that my tent is bolted to slides into a larger size poles on each corner which those are held by the kendorf and locking pins.
R