We looked around from one earlier this year - the symptoms you are describing are similar to my husbands - and we went for a Whill one which is expensive but for several reasons - firstly on the model we have (not a support plus) the back rest can be changed so it could end up more like one of these ones on the link below with a higher back and head rest as things progress, and has an easy to use joystick and also remote controlled operation control, so worked out better in the long run: https://www.tgamobility.co.uk/product/whill-c2-support-plus/