Actually light weight 20C and 25C packs can be made but are not the favorite of the manufacturers because there is a limited market for them (F3A mostly). They simply can't make an economical run in the 1000's of units like they can with the heavier 20C and 25C sport packs. Short cycle life issues with some of the lighter weight higher C rating packs were not the fault of the use but a fault in the design and manufacture of the batteries. In theory, a higher C pack should perform better at all throttle settings due to a lower voltage drop under load and last longer as a normal F3A flight has a rather modest average C draw on the batteries which would lead to lower temps and longer life spans which like Anthony said, it not what many were seeing in actual use.

The Power Unlimited packs for example (shameless plug) are made specifically to our 20C discharge and below 600g requirements while maintaining at least the performance and cycle life of the heavier sport packs which seem to be holding up fairly well but are very heavy. These smaller production runs are more expensive to make - hence the price difference over some of the discount sport packs. We have some 25C -5000 packs in testing (not available so please don't ask) that are the same sub 600g and a real 25C discharge rating. If they work out in our longevity tests, we will sell them but that will be months away and possibly next Spring.

I know this sounds like an advertisement but we really do spend $1,000's on testing batteries by sending sample packs to real F3A flyers who test them in real F3A setups under normal flight conditions. Honestly, we could not care less about how our batteries perform in helis or cars and don't test them that way because we are trying to maximize the packs for the typical F3A type flight usage. Some manufacturers advertise very well, and try to target all segments with their packs, then send out the packs and ask you to do the R&D for them at your expense. A high C rated battery that is also light weight with excellent performance and cycle life can be made but it will never be offered by the high volume discount houses because it is a niche product that requires special production runs and only some are willing to pay the price premium.