This value seems really low as a default.  The default storm configs have the supervisor using a 256 MB heap and each working using a 768 MB heap.  This only gives us space for one worker, assuming that there is no other overhead, and by default there are 4 worker slots configured.  I would prefer to see the default be 256 + 4 * 768 + 256 (slush space) = 3584MB.  Alternatively you could do something like with the VCores and dynamically compute something based off of the number of workers, but have this config be an override for that.