I'm going to have to buy more "stuff" next weekend.I used the webcam this afternoon also but the power was off so they are to dark to be usefull ,I believe.
i'm still not quite positive - are the fenders totally outside of the deck, or does the deck encompass the fenders? looking at the pictures, i'm assuming that you are going to mount your springs to the carrying members that are running the length of the trailer? if so, you are going to have a very narrow track because you can't have the springs very far away from the hubs or your axle tubes will bend easily.
if you are still going to be adding another piece of 3x3 tube at each side to connect all the crossmembers then you would be able to use that to attach your springs to - assuming that the fenders and wheels are completely outside the deck. also, having a 3x3 out there and the 3x3 members as a subframe is actually going to help stiffen things up considerably.