Hello David,
I 've been using your builds for quite a while on my 1900ACSv1.
After r5389 the reghack2, for disabling DFS, stopped working, due to changes of the Trunk sources.
However, there is a user who built a fix for that, but it needs to be included in the filesystem when building the image.
You can get info from here: WRT1900ACS v2 how to update mwlwifi driver
Is there any chance you include it in your next builds so users whose models support it can benefit from it?
(Working models are 1200ACv1, 1900ACSv1, 1900ACv1 & v2)