Lane, we use a wood board under the rear motorplate, and it straddles the motorplate. The belly pan comes up to the motorplate but it doesn't cover it so the motorplate just comes to the bottom on the lower frame rail. We just screwed two pieces of wood onto a wider piece so there is a gap to straddle the alum motorplate. The wood support has a shallow hole in the bottom, and a bolt that it centers on and that bolt is in the trailer floor. This description may not be clear, but hopefully it has you thinking until I can take a picture for you. When we have the wood support in the trailer then we use our racecar dolly [ check included picture] to get the dragster in the trailer and when car is in the right spot in the trailer we just lower the car onto the wood support with the dolly.
We have been towing it this way for 15 years with not chassis issues. The car did get loose in the trailer a couple of times when we had only one tie-down strap on each rear slick, we run double ties now. We have heard of the blow-up bladders leaking also.
I'll take some pictures when we load it up for the Hot Rod Reunion next Wed.
Jon