I do not know about Gixen, but I use Phantom Bidder, and eBay recognises my bids and does not bid against me.  What I mean once I made a manual bid on item that also had BIN (to prevent somebody getting it at the BIN price), then I realised I will be unable to manually bid at the time the auction ends, so I set up Phantom, fully prepared that I will have to pay one increment above my opening bid.  Nobody else bid, and the Phantom did the normal thing placing the 3 bids in the last few seconds, at the starting price.

PhantomBidder gives few free bids, but after that you need to pre-pay.  But the only misses I had over the 8 years were all my fault, like changing my eBay password and not telling Phantom.