Nice piece of work/art you've there. But as I understood it didn't quite work the way you wanted it, I read something about using thinner to make it more flexible. Well thinner, depends on the place you live, is mostly a mixture of xylene/xylol (a benzene ring with to methyl groups -CH3 attached) and, again, depending of the source/store, toluene(benzene ring with one -CH3 attached) and this make it not flexible as you desire. Depending of the composition of the green plank (sorry don't know the english name for it), the polymer/green plank will earlier become crispy/brittle/crumbly instead of flexibel. I would suggest that glue same sized pieces of inner tube of a bycicle tire on the parts shown on photo 4 and 5. Bycicle inner tube is very flexible and maybe this way you can flexibilisezi
(is that a word?) things up.
An other alternative, but this is more rebuilding then upgrading and it's working
find a autosloperij, that's dutch for a place were all old vehicles are brought, a 'car-graveyard' and get the stirring wheel of a suzuki baleno or toy cor, you check. The stirring wheel is steel covered with DEPENDING Of the Brand and Type flexible but durable plastic. But the best thing is the dashboard, difficult for me to explain, but i mean the soft-but-strong 'plastic'covering the front, between the screen and the clockhouse. If you have a big enough piece, proceed as you did on youre photo's. The green cutting board is just a to tough polymer. Greetz and succes!!! (if my story was to hard to follow/understand i can imagine, but please advice how to bring the message better