Hi rtciv,
After a few test runs (empty) the trailer tracks ok, you hardly know its there. Today I done a bit of shopping. While buying my shopping I think I was unconsciously buying heavy stuff - 8 tins beans - Sugar - big bag of spuds etc.
Having loaded up my shopping I headed off to my mates about 2 mile. The trailer handled ok, the bike a little wobbley but I think that happens with all trailers? I cant take SHARP turns due to the box but so far this hasn't been a problem.
When I got home I weighed myself on the bathroom scales - A peanut off
12 Stone 
I then picked up all my shopping and stood on scales again -
14 Stone dead. So my trailer handled
2 Stone today
Just mesured the trailer - Lenght 63in from hitch to rear of tyre. If you look at the picture you'll seen theres a bit of a gap between tyre & trailer, there is also abit of a gap between trailer frame & wheel. I done this as I planed to attach a dynamo to the rear of trailer frame, which would be driven by a chain from trailer wheel. You may just see a small bar in front of the trailer wheel? - this will hold the dynamo/cordless drill motor?
The load area is - Length 20 1/2in X Width 12 1/2 in. just fine for my shopping trips

Should I need to haul anything bigger i'll use my bought (2 wheel) trailer. I also have another long/large haul trailer im still working on...
I wont be able to continue with my BIG trailer (above) until a scource out more materials
Regards
Tom