The uM-FPU V3.1 chip supports 32-bit IEEE 754 compatible floating point and 32-bit integer operations.
Therefore, in a very limited way, it replaces the FP coprocessor with the AVR equivalent IEEE 32-bit lib.
If you download and look at the code you can see that you can customize operation verbs very easily to create any new command or subroutine.
It's just a sample framework written as a calculator. You can create a verb, say HD1, to turn pin D1 High and another verb, say LD1, to turn it low.... and without further programming, a second uC can control digital pin 1. Or... create one verb called D1? and send a 1 or 0 in the stream to parse with Serial.parseInt ...
But to answer the original question, I do not see why you could not offload to a math coprocessor.... surely would run up the co$t for a single-percision FP solution.
Ray