very cool, im starting my 29 as well, this week... i like ur sand what kind is that? also, did u just rest that curved piece of LR to make it a cave like that or did u use some sort of epoxy?
The sand is Caribsea Aragamax sugar sized sand from Marinedepot.com. The arch is actually six fairly large pieces of rock. I used threaded nylon rod and nylon nuts to hold them together. I used a hammer drill with masonry bit to pre-drill the rock so I could slide the threaded rod through. I got the threaded rod from smallparts.com.