Well, got to run the Lexi, towing my Subi, today. De-winterized it and took it out for an 80 mile loop to make sure all is well before first trip in two weeks.
Ran it with my front mount spare tire. 40 miles with the cover and 40 miles back without cover. No difference, temp (via ScanGuage) pegged right at 195-197, interstate, 65-68 mph.
I don't know what the temp without the tire mount was as I hooked up the guage after I mounted the tire, and have no comparison. But I believe, stock, the V-10 runs right at about the same temp.
Extra weight up front is noticable to the extent that the front dosen't feel "light" anymore.