Lior,
In researching the updating of my old maramu's gas/cooking system, I found that Nigel Calder in his book recommended that a propane system could be used for butane but never using a butane system for propane due to the high pressure and that includes the hose, fittings, valves and regulator. He also outlines the gravity siphon of gas from one tank to another as Bill on BeBe explains. Also, when shopping for the newer model ENO stove that I will be installing next month I saw in the owners manual the instructions to change the gap in the burner to accommodate the different gases. When I buy the stove and own the instructions I can post it for you. But Joel has more experience in these matters and if he says you do not have to do it then that's that.
Hope that helps,
Ross