Or you use my ath79 build. All target specific packages are hosted on my server for every build and the repo with signing key is included in the images.
This means, also if there is a new kernel version you could install all target specific packages (kmod-xxx, ...) from my server and never have to enforce a package install with opkg.
Please read the first post in my thread before you switch to the new target.
The performance with flow offloading will be almost the same as for this sfe enabled build.