Sorry if this gets long and I'll try not to ramble too much. I did actually consider running bunks lengthwise to the barge, but...( here comes the rambling part)Shouldn't you have the boat bunk going 90 degrees the other way?
The barge was from a craigslist ad and I was the first one there, so get it and take it home. Now its in the front yard where I know DW will not be happy. Also, I know I'll want an easy way to get it from truck to water, etc. So, I've got this dog cart (like a pony cart) that I made to exercise my dog in the winter when he's not working (goose dog for a private club). He's retired now and the cart isn't needed, so I cut the front end and seat off and added pool noodles to the cross bars. Moved the barge around behind the shed and DW didn't have this unsightly thing in her yard. The noodles split lengthways the first use and I added the carpet. It has worked quite well and I'm still considering changing the bunks, or adding rollers maybe, but the bottom is wide and flat with no keel.