The XR+ seat doesn't have that much support, more than the stock flexi or orig PL seat, but really nothing to speak of. I'd suggesting replacing with
a completely different seat. Check buggy bags (.co.uk) or one thing I tried which worked pretty well was to use a kayak seat with a high back rest on
the sotck PL. There's also a few plans on the forum for adding a plywood backrest. this typically works really well and is cheap and easy to make.
US503 - Manzanita, Oregon
Fixed Bridal: Flexifoil Sting 1.2, 1.7; Rage Acid 2.5m, 3.5m, 4.7m, 6m | Peter Lynn Vapor 11.2m, 16.1m | NPW 7m
Depower : Peter Lynn Venom 2 13m, 16m, 19m | Peter Lynn Phantom 15m | Flysurfer 2.5 SA 19m
LEI : Flexifoil Atom 7m, 9m, 12m; Mutiny 8m
Land rides : Libre Hardcore; Libre v-max; Peter Lynn XR+W | Rollerblade Coyotes! | Ground Industries AK Pro
Water rides : Slingshot Misfit 134; Ocean Rodeo Mako 150; North WAM! 5\'10
4 Sale/Trade: HQ M1 5m, Flysurfer Pulse 10, PL Venom 2 16m, PL Venom 19m