So far I have stained the back and sides without any filling, applied a few coats of wipe on poly with no problems. Use SM clear filler on the top prior to staining this seemed to go ok, it took the water based stain ok not as well as just the wood without filler, allowed several hours for stain to dry then applied a coat of poly hmmm not impressed the poly was still tacky in places after 12 hours, put it in the morning sun which helped a lot to the point where I was able to successfully sand it, phew I had visions (or nightmares) of stripping the poly off and starting again.
Next time I will definitely stain before using SM filler.
Always learning
graham