Hi Jon, thank you for your insightful email reply BTW
Re the Balloon RF modules been too weak to be useful even in LEO I was reminded that David Ackerman's balloon telemetry was received on the west coast of Ireland at a range of 1200KM approx !
I think the distance isn't such an issue but the orientation of the Sat and the fact that 1200KM or much less is very rapidly consumed as the Satellite streaks over head may be more of an issue.
BTW on my Satellite gear search I see that Hackaday have an article on the 50mm on side Sats with even more reduced launch costs.
More importantly following the links and Googling sent us to some Dutch guys who are trying to Kickstart a 5cm Sat that uses a 433Mhz module to send SSTV!
If they get it to work then that kind of proves the point at least as a fringe case
I'll dig out the links and post so folk can have a read !