RM80 Big Wheel

[BadgerMan]

My son has out grown his XR100 and would like some thing with a little higher level of performance. We have considered a KX100 (expensive and scarce) and a CR80 Expert (not a woods friendly motor). The RM80's are very plentiful right now and priced very well. Also, they seem to have a very nice motor for woods riding. However, because of his size, I am afraid he will out grow an RM much quicker than the other two previously mentioned bikes. My questions are this:

Has anyone tried lacing up a 19/16 rim combo on an RM80? How did it work? What parts were needed and where did you get the parts?