Hi Frank
With the 818 at race height it can be a real pain getting on a trailer.
There are a couple of place you get in trouble.
1. The nose on the approach to the ramps. If the nose is 4" and 3 ft in front of the axle. You need a ramp that rises less than 4" per 36".
So your 17" trailer divided by 4/36 = 153" or 13' long ramps.
As the middle of the car goes top of the ramp, the problem is even worse.
Lowering the tail of the trailer definitely helps. We have actually taken the wheels off the trailer and set the hubs/drums on the ground successfully.
In This picture, I put smaller wheels and a drop axle on my trailer.
Just as a side note. The CG of my car is right about at the door striker plates.
Bob