This could create problems on systems where the memory limits are (very) strict. This is the case on our login nodes, for example.
At some point, the heap is created twice (Java >_<), so you actually need to count this at least double to see whether it is a problem.

I haven't seen any issues with not having this set at install time, but in any case, we should try and avoid hardcoding any value here...
Maybe we should use something like `${EB_MATLAB_JAVA_XMX:--Xmx512m}`, which makes it at least easily customizable.