Is there a way to disable 5GHz on the LWB5+

You can disable 5GHz on the SDIO version of the LWB5+, by modifying the NVRAM file (i.e. .txt file in /lib/firmware) as follows:

change devid=0x4418 to devid=0x4419

Note: This is currently not possible on the the USB version on the LWB5+ because the NVRAM information is included in the firmware.