Ah yeah I was assuming the amp had a couple of parallel outputs and selector switch for the ohm rating. You could probably run them in series from the 5ohm output furthest to the left, but might not be worth it as your 8 ohm cab will be doing most of the work...the extra load of the second cab probably won't add much volume but could damage the head.
Best to work out the combined load of the two cabs and if it exceeds 5ohms, I wouldn't risk it!
Ah yeah I was assuming the amp had a couple of parallel outputs and selector switch for the ohm rating. You could probably run them in series from the 5ohm output furthest to the left, but might not be worth it as your 8 ohm cab will be doing most of the work...the extra load of the second cab probably won't add much volume but could damage the head.
Best to work out the combined load of the two cabs and if it exceeds 5ohms, I wouldn't risk it!