prior to vexos 1.0.12, stack memory was limited to 8k per thread (not an uncommon amount for an embedded system). vexos 1.0.12 changed that to be somewhat variable based on the number of threads created and could potentially be as much as 512k, however, if you need large amount of memory either use global memory or allocate it on the heap using malloc or new. If more heap memory is needed in VEXcode, you can modify the standard build files as explained in this post.