I wouldn't worry too much about making the transaction to a longer trailer. I had the same fear about making the transaction from a PUP to my 29' TT.
I had some experience pulling long trailers in the Army but it had been years since I had done that. In my opinion, short trailers like those for small boats and utility trailers are much harder to back (and jack knife) than longer trailers. If you have a tight place the trailer needs to go in (like a driveway) that maybe a consideration. Once you start towing and backing a longer trailer and get the hang of it, a longer trailer isn't much different than pulling a short trailer. You have to watch your turns and swing wide at times but practice will make it easier over time.
