I have an Esprit 120ED with 0.77x Reducer/Flattener (the new one). The scope itself is originally f/7, and its reduced to f/5.39 with the reducer.
Using 1.25" ZWO RGB set and 1.25" Optolong Narrowband set. There is no vignetting with this setup, so I wouldn't expect any on f/4.9, or maybe just minimal.