I think I've discovered a big fat exploit.
A nifty new feature for 2.5 is that a race can gather sensor data on tech systems that they can see. This is converted into RP's, which can then be downloaded into research centers. This is a very cool feature, but it has given me quite a bit to think about in terms of letting other races get close to my ships/bases.
At any rate, RP's are gathered for individual systems, like, say, "Fire Control Speed Rating 4,000 kps", and the RP's gathered are subtracted off of the total amount of RP's you have to research to develop the system.
The exploit is related to the fact that you can continue accumulating RP's for that system even when you've accumulated enough to develop the system. In other words, the amount of RP's needed to develop the system will go into negative numbers, and when you do develop the system, those negative RP's will be applied to whatever you develop next. Free RP's!
The solution is either to make sure that no research project can have negative RP's, or, when any given research project reaches zero or negative RP's it is automatically developed rather than having to wait for the player to schedule it for R&D.
Kurt