I am helping a friend to build RV12. We are remaking static line and could not source tygon tube 1/8 locally. He insists on reordering. Could we use 1/4 line or it's forbidden by the Book of LSA?
The DAR would never catch that but technically you should stick to the plans.
If he or she did, it was only because he reads this forum.
So far the kit that Van's supplied has been great with no problems.
Go ahead and use the 1/4 inch. Nobody will know or care about the difference. In my opinion, you will have a superior installation - the 1/8 inch tubing is very prone to kinking or being pinched by the tie-wraps you will use running around the frame to the ADAHRS.