Just came back across this thread. August 2016 I got a flask of Prosthechea karwinskii from Marni Turkel. The website said that she tries to get 25 seedlings in each flask. I potted them up in three "vigorous" compots and one compot of the "runts."

Almost a year later, I've sold and donated two of the compots. I kept the runt and 1 vigorous one. I've mounted or potted up 15 of the strongest growers and even the runt compot has several strong growers. Oh and I think overall there were at least 60+ in the flask and all of them made it!

Now I just need to wait two or three more years to figure out which ones are the strongest most fragrant bloomers.