Generally speaking, the technical data for each model indicate the approved weight ranges. You can find the technical data on the respective product pages. The “sweet spot” in terms of pilot weight/glider size depends a little on personal preference and the planned use. Examples: vol-biv flying with a lot or a little luggage? Dynamic or normal flight behavior preferred?
UP designer Franta Pavlousek has some tips for choosing the ideal size:
“If you are in the middle third of a weight range for an UP wing, then you have already found the right size. If you are between two sizes and are wondering whether you should fly the smaller size in the upper third or the larger size in the lower third, then it's best to proceed as follows: If you are an experienced pilot and have always flown in the lower third or upper third, you should also choose your UP wing accordingly. If you generally prefer to fly with more weight than less, you should choose the smaller size. If you prefer a larger surface area, there is no problem in flying the larger size. It's really just a matter of preference. The wing will still fly fast and have precise handling."
Even if you do a lot of flying in flat terrain, you will probably be right to choose the larger wing. Those moving up in class are also better off choosing the larger size. Then the jump, for example from EN-B to EN-C, is not quite so huge.
As the UP development team, it is our philosophy to maintain all the features that pilots love about one of our glider series in the next generation – supplemented and improved by our input. This makes our existing customers happy and therefore makes us happy too. If you fly an UP series, you can be sure that the successor will give you the same handling that you are used to.
IMPORTANT: If you have been flying an older UP generation wing (up to and including the KANTEGA XC, SUMMIT XC, TRANGO XC, EDGE or any of the TARGA models) and you want crisper, more accurate handling, then it is best to fly the new model at the upper end of the weight range. If you want to get closer to the feel of your old model, you should go up a size.