Be careful of a 6' wide trailer for trikes. Some trikes will fit some will not. You have to measure between the cables that lower and raise the ramp door to know what will roll up the ramp.
I have a 2010 HD Roadglide with a Motortrike conversion and it will not fit between the cables of most 6' wide trailers.
I bought a 7x14' tandem and I have about 5" clearance on each side of the cables
I put a 4" strip of black stair tread in the center of my ramp and trailer up to my Biker Bar hold down system. This keeps me totally center in my trailer and between the cables.
I also put 8" wide Black Stair tread up my ramp centered on my rear tires. This really helps you keep from slipping when loading in the rain or just wet pavement and tires. The paint on the ramp can get very slippery when wet. I had a very bad day loading my 2 wheeler on a wet ramp one time.