The TT40 Pro is the engine most used for AMA 424 class of Q500 (quickie) racing. Some areas of the country use OS 46s and maybe a couple of others. The scat cat fits the AMA 424 category. Your 40LA will fly the plane fine but unless every body else is using the same engine you are going to get beat bad and often. The TT40 is a fine engine at a good price. The plane will fly great on anything from a good 25 up to the 50s, 52s, 53s, 54s and 55s in 40 size cases. Get together with the other guys and pick an engine most have or are willing to buy and is readily available where you are, spares included.

Denis