I once asked the best refrigeration man I ever met about refilling propane
bottles.  Since he dealt with all manner of bottled gases in his trade and I
knew he refilled a few CO2 bottles for his buddies with Beermeisters , I
figured he would know of such things.  His answer was something like, "It can
be done, but why risk blowing up your sorry ass just too save a couple
bucks".  With that, I had heard all I needed to hear.

Rich