I don't think you could cut them down AND have them look nice. The end you cut will be straight and the other end rounded. It is just aluminum and plastic so the actual cutting would be easy... the appearance would the issue if it was me. The boards are 105" long, not sure how much space you have between your wheels.
Yeah.. i see now. The Arch Amazon set up I went with, they had 'end caps' which were removable. 2 screws/remove/cut/ replace end cap. By your pictures, Quest4adv, may be able to fit them on their 136"
Just gotta measure.
All the links to the products are in there.
Its a long thread but very easy to read and follow.
BUT.... now it seems that the boards and mounts in this thread are cheaper!
Look at sonic6 photos andyou can see that the boards dont come closeto the rear wheel.
That make me believe that they will work on a 136wb.
Its my guess that they will.
Ill measure for you.
My boards are aprox 90incheson my 136wb.
Aprox 10inches to the rear wheel from the end of the board. So, you can probally do with a 100 inch board.
Sonic6 says his are 105, so you're probally SOL.
Unless contact the MFGR and beg for a pair that'll work for you.