NPG, if you have the same MEC front platform rack I have, it might be a little too light-duty and a little too high-riding for heavy loads at high speeds. So far, I've used mine mainly for shopping -- about 10 pounds per side, tops -- and I've never had any tracking or shimmying problems. But I haven't gone screaming down any long, steep hills either. I'd go along with those who suggest shifting more weight to your rear rack. Also, try to pack the heavy stuff as low as possible in your front panniers. You might try low-riders up front, but I like the front platform rack for its convenience and versatility.
Last edited by marmot; 06-05-11 at 10:16 PM.