I have been carrying my drz-400 (about 300 lbs) on a front hitch rack for a few years and about 10k miles. No issues at all. I just drove from CA to WY last week and had to go through Utah with 108F heat and my truck was not overheating with the bike on the front. It does block the headlights slightly but it still illuminates the road ahead.
Personally, I like the front better because I can see what the bike is doing if I hit a hard bump. Also, I find it easier to park when I can hang the bike over vegetation or into a bush. Can't do that with the back mount and still use your door!
I would suggest that your tie-downs have carabiners (not hooks) at the end of the strap. I had one time that I hit a hard bump and one of my 4 tiedowns got enough slack for the hook to slip out of the hold on the carrier. If the bike wasn't on the front I would not have quickly seen a strap loose tension.
Hope this helps