because Windows 3.1 is a 16 bit system, you can use only <64K in a simple segment. The solution is similiar as the Dos one: use a 32 bit extender!
Under Dos, there is a variety of 32-bit extenders like TNT, PharLap or DOS4GW, which I personally prefer (because it was included with my Watcom C++, "royalty free"). Similiary you can use Watcom's own WINDOWS EXTENDER, which allows you to have a whole 32 bit Windows environment, eg. int is then 32 bits wide, you don't want huge or far pointers, etc.!!!
The extender is also included with Watcom C++ 10.5 (simply create a Win386 target...)