IBQUILTIN

I think you could piece the pieces of insulation board and hang them gently with Command Strips until you can finish it the way you want it. I agree with the others, I have 2- 4ftX8ft sheets on my wall and it often is not big enough. Think I'll start doing smaller projects

Jane Quilter

Have you looked at "Heavy duty design wall" By snowbird posted on 5/16/2016? She uses the whole wall because she starts at the top of the wall, and doesn't use styro boards, Worth a look.

bearisgray

A thing I would hate to do - but my DH might cooperate if I did -

Admit that I goofed and ask him for help.

Occasionally, a DH has a really good solution for a problem. (Mine will usually come through - after some grumbling - )

Onebyone

I would buy another board, cut it in half, cover it and then staple it to fit flush with the other one. A staple or two on top of each piece to hold it to the wall won't leave any noticeable holes in the wall.

osewme

If you don't have a way to transport a complete piece of insulation board maybe you could get Home Depot/Lowes to cut it for you for a small fee so it would fit in your car.