I use Xara for some of our wrap layouts. You don't need 300 dpi at full scale! 72 to 100 is plenty and you won't tell the difference. I typically do the layout 1/10 scale and export at 720 dpi. I can't explain the difference that someone explained to me once, but just do a small test print and you'll see what I'm talking about.

here is a link to some of the wraps we did, all designed in Xara, at 1/10 scale and exported at 720. (for 72 dpi at full scale) includes some close ups.

http://www.sharxskinz.com/#Sharx%20Skinz