Not sure your expectations are right with this one!
Sounds like your tow bar on your car is is too high and you need a drop plate to get the tow ball to right. See here - http://www.landyzone.co.uk/lz/attach...190411-002.jpg
It's not correct to say you can't move the axle location etc without loosing type approval. They are designed to be altered to fit a particular hull shape and they certainly don't come 100% set up for your particular boat - no matter how much info you give! They are supplied as is and you just have to adjust them yourself I'm afraid.
I had a DeGraffe a while back and it was a good fit after I roughly described the hull on the telephone but that's just luck not expert adjustment!! The 2 Indespension ones I had were miles out with the rollers just at the very edge of the beams with no attempt to put them in the right space.
I have now bought 3 SBS trailers, only ever had one problem and a free spare was sent immediately the next day, the rest were flawless. South West Boat Trailer have supplied all of em to me, all at good prices and no problems.
Bottom line it sounds like your trailer is fit for purpose it just needs adjustment.