Hi Rob,
Which USB WiFi dongle do you use on your BF526 board? Did you get the 20Mbps performance and 8k interrupt frequency in the 2012R2 release?
The interrupt frequency is decided by the hardware IP. The MUSB IP in BF526 has only 1k-byte fifo in the tx end point. If you want fewer interrupt, the MUSB in BF60x is an option, which has 8k-byte fifo. Could you try your application on BF609-ezkit?
We don't recommend customers to use trunk head kernel, because they may have unknown bugs. Please use the 2012R2 release instead.