Another option I think would be to forward mount a 24 on the quad bike and fit a pair of castor wheels on the front of it. .
Oh Norm, you never miss a chance to push the virtues of a Super 24 now then do you ;-)
Seriously though that would be a step up from a 18" towed backwards (seems from personal use mowers always cut a lot better moving forwards then when you do the bad habit of cutting pulling backwards). It'd be a great little project to follow on here as well.
Love the outside the box thinking to solve a problem so simply and with what was essentially already onhand, rather than going to buy a Grillo etc for a fortune.