We place the frame on the car and make all the needed adjustments first
before we install the top. It's too late once the top is on. One of those adjustments is the back hoop which will move fore or aft enough so that you can center the latching pin. I've also seen where the pin can be bent, sometimes a great deal more than you might expect.
The fabric material doesn't shrink per say, the rubber membrane does, which I suppose could be considred the top. I've seen tops that weren't up and latched for years and the owner came to pick up the car and we had it latched front and back, much to their surprise.
I don't slam anything, it's a good way to break stuff and I frown very heavily on that around my place. I won't slam the hood either, or a door, or a trunk lid. I close it carefully, pull the saftety catch back by hand, and then push the hood closed with the palm of my hand. If I catch anyone slaming hoods around my place they might find my steel toed boot slamed into their ass.
Anyone can leave tools in the engine bay that can leave some mighty fine '' outies '' in the hood. I have to pay for it,
and, it's not cheap work either.
Anyway, back to the soft top. If it won't close because it's too tight I latch it at the back first and then go to the front. It will take two people to do this but you can carefully pull it forward enough to start the gear and then leave it loose. Go to the other side and do the same thing and then carefully turn the handles to lock it down. Leave the top up for a long time after this and it might relax a bit over time. If it really
is too tight, this won't work but most of them will latch if you work carefully.
The reason this works is because you can push a lot harder from inside the car with a bit of help from outside of the car than you can at the back - it's just more possible to do. At the back latch it either hooks or it doesn't and you can't put all that much force on the middle of the top while standing and leaning over the car. If the top is new and adjusted properly it should close easily with moderate pressure ( no real need to slam it ) and it will close at the back as intended. Older tops may not close easily and then you should go to the front if it looks like it won't happen. This also works better on early cars than it does on late ones. 280SL's have those padded mouldings around the window frame that require extra care not to dig the gear into. This is why you really need two people to do this so it can be pulled forward properly. If you don't have help and you're not sure it will work, DON"T EVEN TRY!
I have seen where the rear window would split because it was so old once we got the top fully latched down. Only a really screwed up top will do this so you needed a new one anyway. :'(
Anyone ever drive with the back of the top pulled forward? Kind of like a Targa with the back open. Works OK actually.