Ive got PVC to conform to some tricky shapes. If you are set on leather, then ignore the following.....
I made some internal GRP/PVC door skins and trimmed the rear bulkhead in PVC instead of using carpet.
DSC00591 - Cobra Club Gallery
crendon door skin test fit - Cobra Club Gallery
- hopefully these pics are visible.
if you use PVC, first spray a flattish centre section and stick it in place.
Then 'borrow' your wife's hair dryer and gently apply heat front and back on the PVC - get it pretty warm but not uncomfortably hot to the touch of your palm. When you've got the heat into it, gently pull it round the curves you want it to conform to, WITHOUT adhesive. Of course it wont lie neatly because you can only pull in 1 direction at a time, and most likely you have some compound curves to deal with. Once you have pulled it (it can help a lot if a friend can help steady the centre section), spray the rear face and using a bundled up cloth or very small towel, gently push the vynil into where you want it, pulling the edge gently, as needed. You will need to work around the curve, pushing with the cloth, and pulling with your hand, as you go. Dont wait for the adhesive to go off fully, as you may want to pull it off and reposition it to make it sit neatly.
If its a concave curve, push it into the crevices. I use a flexi-curve from my old technical drawing class in school thats bent round to push the vynil into the curved surface.
If its a convex curve, you will need to work it round - this is where your friend's hands comes in handy making sure the centre section doesnt get wrinkled or tugged.
Have some shears handy (I use aero snips) to cut slits near the boundary - this helps eliminate wrinkles and overlaps. But it also helps if you can minimise the amount of excessive material: about an inch overlap is good idea, but go for more than this initially as its too easy to get your estimates of coverage wrong. You can always cut more, you cant put it back when its gone. When happy, the slits can be made into triangular cuts that can then be wrapped around the edge. I haveto have a couple of goes at this part to make it sit neat around areas of high curvature - Im not a professional trimmer.
When happy, clamp up in position as much as possible and leave over night to dry. Use telephone directories and wood to apply clamping force across a larger area. Dont over-tighten g-clamps, only gently pressure is needed - otherwise these will leave an impression in the vynil that wont shift.
Finally: PVC is cheap. If you get it wrong, walk away, have a beer, come back next day and try again. On one of the above door skins I had to have 3 goes at it before i was happy.
Hope that helps.