I have the same setup and I am looking to buy skins too. A guy at a mountaineering shop told me that some glide better than others, however, the ones that glide better may not climb as well. He didn't say the differences were huge and with the width of the Mantra any skin will climb well. To those with experience with skins...does the tail attachment differ greatly and if so, what's better for a ski with a slight twin tip?
I have Ascension Glide Lite with STS tail attachment system. The 120 size will give full coverage, and 110 can be used with a few cm of tip exposure, but still very functional. I have not had any problems with snow sticking to my skins, but there is a wax sold that you can rub on to improve glide and prevent slush balls from freezing. Glide lite came with cutting instructions and blade, separator strips and carrying case. The tail attachment has worked well and there has been no slipping to this point.