We load ours when not hooked up often with no problems. I don't raise the front unless there's a down-slope behind the trailer. Have hung up the bottom of the bike a couple times where the ramp meets the trailer - not a fun time! Also I have turn-downs on my mufflers and if the ramp is too steep they will hit the ground at the bottom of the ramp when backing off.
I found out it's most important to make sure the ground is relatively flat behind the trailer to avoid problems. There's some adjustment possible with the beaver tail ramp, but not a lot that will do much good either at the top or bottom. Sometimes we have to drive the trailer and bike to a spot where loading and unloading will work better.