Vello Universal Softbox for Portable Flash (Large)

what do you use to power your Sunpak 522?

It will be a little tight but should fit.

the flash is good the soft box is a piece of junk.

Yes it will, however, the velcro strips that come with the softbox are small, I used some larger strips from Lowes (Home Depot has as well). Use this on a Canon 430 EX II mounted on a Kacy pole to give soft light on outdoor flower photography. Once the velcro is on the flash it will not accept an Omni bounce diffuser or similar item without removing the velcro, so plan ahead if you want to switch diffusers in the future.

By exposure sensor, do you mean you are using a thyristor type flash? If that's the case, I would say probably yes. It may also interfere with optical sensors on flashes with the sensor on the front, but you can usually swivel the head to address that concern.