Good news! Daniel and I have finally come up with a solution to our caster problem: rebar! For those of you who don't know, rebar is an extremely accessible, dirt cheap, building material, found everywhere in third world countries. Rebar is long and skinny, and very durable, and it comes in plenty of sizes. Daniel and I were able to find 1/2" X 48" at Lowe's for a mere $2.98. Our casters need to fit in a 5/8" hole, so we think the rebar will fit perfectly. Sometime this week we'll go to Lowe's and then we can begin fitting the wheels on our wheelchair again. Hurrah! Another challenge overcome!