Posted with the permission of GavinFuzzy.
This replaces the standard SPAMF magwell and magazine releases. Side-plates attach with two 4-40 screws each and the release is tensioned with a short length of elastic.
Basically I started with CaptainSlug's T4 magwell and chopped it down until it fit the SPAMF, then copied all necessary bits over to attach it. It uses one fewer attachment lug than the original, so if durability becomes a problem I can try to add more attachment surfaces through the old magazine catch holes.
The author hasn't provided the model origin yet.