As an update, I'm now leaning more towards doing a 14.5 inch or 16 inch midlength build. Engage has one of the Spikes Tactical pinned 14.5 inch uppers in stock and it's rather tempting.
With the 16 inch midlength, I'm thinking of doing a mock dissipator style upper.
Pic from intarwebs provided for those not familiar with the mock dissipator style:
With the 16 inch midlength, I'm thinking of doing a mock dissipator style upper.
Pic from intarwebs provided for those not familiar with the mock dissipator style: