Try these settings for the beacon period, rts threshold and fragmentation threshold, the rest are what I use and have always used. I'm not getting 300, but 130, where I got 300 before, but my speed has camu up some and the signal more stable. I still wish I could go back to 1.21, it was much better.
Transmit Power - High
Beacon Period - 80
RTS Threshold - 2100
Fragmentation Threshold - 2100
Dtim Interval - 1
802.11 mode - n only
Channel - 11 (or other)
Transmission Rate - Best (Automatic)
Channel Width _ Auto 20/40
Security Mode - WPA-Personal
WPA Mode - WPA2 Only