I do pretty much the same thing, but two suggestions: First, attach your line to the jib halyard (instead of the forestay) and through the pulley and then tie off on the mainsheet cleat. Makes it alot easier to pin the forestay without a line, carabiner, whatever, in the thimble. Also, you can put your trap wires around the front corner castings and this will give you a little more stability side to side when you're stepping the mast. Plus it keeps them from snagging on anything (trailer, rudders, etc) while you are solo steppiing.
I've been doing it this way for a couple of years now and never had any problems.
Kirk