In an message to the aolserver list in mid February, Jeff Hobbs mentioned something on the order of his feeling that all tcl threads need or would benefit from a large stack.
The openacs lore has been that 500K has been the appropriate stacksize.
I added that warning in myself after getting enough reports. I narrowed the size to 2400K to match the default Tcl eval stack recursion limit of 1000. I think 4M is more than you need, 1M will likely do it, and 2400K covers all the bases.
Jeff
