There are a few possible problems depending on unmentioned aspects. The spacing between the rings will likely not be what an indexed system wants. With a narrow chain this C_C dimension might allow the chain to ride up on the small ring's teeth and spin/slip with out engaging then. The chain ring bolts might not tighten down fully if their too long. Only trying things will tell for sure.

Having said that I run as much on a few bikes, but I use a non indexed shifter for the front and know how to shift better then most. Andy.