I use 3/16 now. It just sucks trying to get it over fuel filters and petcocks. Even with heating and oiling, it's an endeavor. I'd rather go for 7/32, or 5.5. I believe that you still don't need to use clamps with these sizes.
Thanks for the feedback...I'll stay away from vinyl and keep looking. Seems like trying some local machine shops may be a good idea.