Q5 will struggle especially with the 2.0T engine. The Touareg or Q7 TDI are the way to go. both will handle most mastercrafts well.
If you get the Q7 or the Porsche get the Air ride.
2008 Mastercraft 40th Anniversary X-star
2008 Touareg V8 Galapagos Metallic, Sienna leather, Execline, Technology pkg, Sports pkg,Class III hitch.
2012 Volkswagen GTI 5dr DSG, Carbon Grey Metallic w/ Leather/Luxury, Technology and 18" Serron Pkg's. H&R springs, Unitronic Stage 2 Chip, Ultimate racing 3" downpipe w/200 cell metal cat, xenondepot 3k HID Fog lights.