Whilst I can appreciate Pidgeon is going from Tramp~ to PJ's I'm the reverse, going from PJ's to Trampolining.
I found the difference between the two is immense. The first jump I did on a Tramp~ was very different to a jump on PJ's.
I'd say to prevent doing yourself an injury is to re-familiarise yourself with jumping on a trampoline whilst improving on your PJ's. To start with you'll need to break them in otherwise if you put so much force into them to get air you could break them fresh out the box, they do need to be softened up.
Slowly does it, theres no rush!