I live on the 4th floor of an apartment complex in a rather urban area, so unfortunately I don't have the option of using a propane setup without doing something very stupid and/or illegal on the patio. I'll do a test run tonight just to get a ballpark time of how long it'll take and to see if it's even possible. That being said, the pot fits perfectly over two burners, so who knows.
I don't think you will have a problem. I have done plenty of full boils on two burners of some pretty funky old electric and gas stoves. Maybe ended up a little darker than it might have otherwise but never tasted scorched. It might also take longer so there is the issue of continued conversion of the partial mash part. Until it reaches a temp sufficient to denature all the enzymes your wort will continue to convert and thus get slighly more fermentable. But not much I would think.