If @Laurent.O needed the extra performance in the mean time, would using vm-eval to access the Chez Scheme FFI work? Or maybe it would be better to write a Chez Scheme library and access it as you explained in Calling into a Chez Scheme library from Racket -- imported symbol rewritten in vm-eval? - #9 by mflatt? Or do those e.g. inhibit inlining such that it wouldn't pay off?