I gather you are running the bike into the A frame, my heritage diidnt fit in my trailer and it was 2380mm.(almost 8' At 7' the bike will have to be on the angle. I built this trailer for dirt bikes with one bike forward into the box on the front, should have made the recess wider to suit a heritage guard and then the heritage would have fitted on. This trailer had a full width tailgate but with 4wd tyres on it I had to lift the tailgate off the ground so that the bike rails would not scrape at the top. Good idea with the dropped axle, means better clearance.
When I built this trailer I tested it by sitting all the dirt bikes on the floor/platform with a length of 2 inch pipe underneath it. I then moved the platform back and forward till it was balanced, that is where the I placed the axle. I also set up the dirt bikes tie downs with metal rod instead of straps. No more worrying about fork seals or bikes falling over. This was easy as I made small brackets up that bolted on to the trees with a hole in them to take a 3/8 bolt and nylock nut. Doing this and making it look good on your bike mate will be a lot harder. Hahaha
Mine is a 7X4 with extended front over the draw bar, I use it for the Fatboy and the quad bike.