<i>Has anyone ever used cyclopropane, as it wrould have more energy avalible, because of the break down to normal linear porpane then the normal energy released via oxidation.</i>
Hell, while we're at it, use ethene. Or Propan-di-ene would be even better.... Oh, wait, that's what you get in MAPP gas.
There are certain limits to safe fuels- when you start involving double/Triple bonds and ring structures things get risky. Try and avoid them... When you reach Ethyne (Triple bond), you get serious risks.
Most of you will know Ethyne as Acetylene.