MWI over Qsig works with option 11. So it should work with option 81 as well. Have you followed the interoperability guides for QSIG integration? You will have to possibly do some tweaks but it will get you there 99% of the way.
QSIG is the way to go and I highly recommend that over PIMGs, you will have to troubleshoot that set up as well, not plug and play either.
The PIMG integration guides are also on cco in the interoperability section.
Let me know if you don't have the link.