I would tend to agree with the dont spawn VT. I sourced CTs and PKs and did not have any problems rehoming the youngsters via EBay UK - people are prepared to pay postage and packaging for quality fish.
I use the same heater whether tank is full or not as long as heater/stat is fully covered(Although I have found I have to adjust setting as I raise from spawn to rearing level). I suppose like many others I risk the stat sticking and overheating the tank although in 30 odds years it is yet to...