phil ,if your interested i have a set of those 7200,the ones i used at the wlrc nationals,they did 4 meetings total and put into storage at 6.7v,£90 for the pair,im still using my hpi plazma 6500 been using them for 19 months and still show no signs of swelling,although they have dropped a volt or 2, ill be getting the hpi lipos again when i feel i need to change them
are you letting them cool down before you recharge them?
i had the same problem with some shorty ip lipos