Hi Francois,i also suffer with spondylitis and was really struggling with my back foot launching especially the nxt day which was really painfull
I bought a pap moster and pap trike so can use motor on its own for foot lauch or attach trike to motor if my backs starting to play up trike only takes couple of mins to assemble
Trike packs up into its own bag and fits into back of my fiesta along side motor so very easy to transport
cheers jon