Thought you might find this article on balsa fillers and strength/weight useful: https://rocketn00b.blogspot.com/2018/05/balsa-grain-fillers-and-added-weight.html
It seems to agree with you that a glue coating adds a lot of strength (though a paper and glue combo also tends to add a lot of weight). Interestingly making a white glue and water slurry with talc as filler (and no papering) appears to really strengthen balsa with less of a weight penalty. Having said that, in your situation I'd prefer strength over weight too because of the strain from the motors.
Rktman, There is a lot of detailed information there. I think I would agree with you that strength is pretty important for my application.
Frank, I did use iron-on monokote years ago on the Estes AstroBlaster and Dr. John Kallend's LadyHawk years ago. The finished product looked very good, but I spent a lot of time working on the monokote. I am so far happy with the balsa white-glue coated label paper.