Having tested this now. It works.

Obviously will not recommend this to run permanently.

The reason for the duct tape is because the L3 Boards are slightly too long and hang out stopping me from screwing the back fan on.

I also had to chop off the PCI-E Power Connector Locks.

Obviously using the D3 Chassis only 3 L3 Boards can fit. But this works and is mining Litecoin.

 

https://image.ibb.co/iN3v96/d3_l3_hybrid_1.jpg

https://image.ibb.co/gS5mGm/d3_l3_hybrid_2.jpg