I'm not sure I follow what you're trying to do. I'll try to paraphrase:
Your primary pool is an "other" pool with some port specified in the Port text box (let's say 8333).
Your backup pool has a different port than 8333, let's say 8332.
For me, I am able to put it in the extra flags like this and have it work:
--backup=Kiv.GPU:mypass@api.bitcoin.cz:8332
The port for the backup pool is supplied by me after the colon, while the port for the primary will come from the Port text box. Let me know if this helps at all, maybe I misunderstand or you're having a different issue
Your primary pool is an "other" pool with some port specified in the Port text box (let's say 8333).
Your backup pool has a different port than 8333, let's say 8332.
For me, I am able to put it in the extra flags like this and have it work:
--backup=Kiv.GPU:mypass@api.bitcoin.cz:8332
The port for the backup pool is supplied by me after the colon, while the port for the primary will come from the Port text box. Let me know if this helps at all, maybe I misunderstand or you're having a different issue
I seem to fail at using a pool with different port as backup for an "other" pool. It appends the port specified in the field, and leaving that blank makes poclbm refuse to start so it doesn't help adding the port for the main pool in the address field.