FYI, the stock rx box isnt water tight anyway, and no-one with any sense/ respect for their property would drive a sensitive BL system through any kind of deep puddle or shallow stream etc- water and electronics dont mix. As it is (funny part), traxxas wont warrenty water damaged parts on their trucks, so it shows how much faith they have in the 'water proof' rx box and servos.
I understand its frustrating that the stock rx box wont fit, but its ugly anyway, and the FLM one was designed to be sleaker and more compact- the stock rx box is also huge, as is the stock rx, and most upgraders would be be using a better radio with a smaller rx- hence the smaller gap between the servo locations. In addition, jholthus does seem to be using stock steering parts, just different (decent) servos, so it shouldnt take too much hassler to make the setup work with stock servos.
Or, to look at things a bit more objectively, designs evolve and get tweaked as potential issues get identified by users who have a miriad of possible setups, not all of which could be tested by the manufactuer to ensure compatibilty and reliabilty, eg:
MMM is on its 3rd incarnation (V3)
Hybrid revo diffs are also in their 3rd incarnation.
Emaxx has been tweaked and upgraded half a dozen times- several times in the 3906 format.
Tmaxx has been altered god knows how many times, same too with any r/c model.
Gotta cut FLM a little slack- they responded to customer feedback and altered the design to make people happy, thats alot more than some companies do