I finally had time to modify the magazine to feed. I only had two rounds to test with, but got both to feed without issue. Field tests still to be conducted.

First step was to lower the front lip of the MDT 223 magazine to fit under a 'chin' of metal below the feed ramp in the magazine well

https://imgur.com/28nYzGD

The bolt was then hitting the rear of the magazine 'lips' and they angled to allowing feeding.

https://imgur.com/QvWpisU