>Our code is a few thousand lines. A large part of the code does a complex simulation of a user-defined manufacturing process and walks through the process (sometimes 500 steps) taking branches and iterative loops, determining labor needs, equipment usage, number/cost of units produced, etc. My head swims at

That seems to be the part where FoxPro can't beat C/C++. There are dozens of things that can be optimised in C vs. FoxPro when it's about calculations.

Vlad