Seats are fraut with things to go wrong. basically , trimmer see a good job of retrimming a seat as being no wrinkles in the leather … personally I go for comfort.
But to get the wrinkles out they pack up the stuffing with foam [ a bit like a balloon.
Which means the driver sits higher. Much higher.
2 examples , the new owner old E Type had the seats re-trimmed by a well know motor trimmer
When I tried sitting i it my head touched the head lining and likewise room was less all round.
Second case , an SS saloon came to us part restored. The seats had been done in another state. Nice looking job , but when in the car and sitting on them , my [ and the owner’s] heads touched the roof , and that’s without a head lining in.
With a MK IV one also needs to be careful the trimmer doesn’t make the seats any wider as there is no wiggle room against the door… And for the same reason , the door cards/ backing must not be thickerthan original and the padding under the leather cloth no thicker than original. Otherwise getting the bezels over the handles can become impossible and the door trim will be pressing on the seat.
The whole thing is an example where you need to be tight control of the process and not let a trimmer , who may never have seen a MK IV, take over.
Ther e are two different types of seat , pleated and un-pleated. The pleated off better support , But the frames are different and one can’t be converted to the other.
The original seats had long coil springs under across the frame. Then straps which supported coil springs and the padding [ wool] and horsehair…
Trimmers now will use foam in varying degrees of hardness. I would get a seat into the car and try sitting on it between this stap and the leather covering
IF pleated , the pleats should be the original profile., The pleats are mad eby sewing then padding stuffed up in them
The shape of the pleat depends on how much and what thickness. They should not be overly pronounced.