Just one more tip, which you may have figured out already, but if not...
When your proxy bid has been pushed up to less than 1 increment of bidding, the underbidder KNOWS that your are sitting exactly on your maximum bid. If no one else comes along to compete for the chip, the underbidder can snipe your chip with just 1 more increment bid at the last seconds, and may be tempted to do so.

For example, let's say you start off as the first bidder with a bid of $12.00 on a $9.99 starting bid item. Your bid will show as $9.99. Another bidder comes along and bids $11.75, so your proxy bid leapfrogs his bid to your max of $12.00. Since the normal bid increment is 50c, he knows that the only way your bid did not go to $12.25 was because $12.00 was your maximum. Now he knows for sure that he can get the chip with one more last-second bid of $12.50, assuming no others are in competition. If you ever see that your high (proxy) bid is less than 1 full increment higher than your posted high bid, you know that the underbidder knows you're at maximum.

Depending on how much you want the chip, you may want to increase your own maximum bid (even though it will complete the increment) to give your high bid some privacy.