I am afraid this is not an encouraging reply.
If the item is rare and those after it are serious collectors, they will tend to be snipers (except German collectors, for some obscure reason) and will not show their hands.
I faced exactly this situation with a 1932 Schneider Trophy air race catalogue with original lap times pencilled in making it truly rare. Hardly a bid on it when I first noticed it and standing at around the £10 mark. I had not seen another one (though you can buy a modern reprint) In the end I just had to guess what I thought it would make. I also put in a manual bid just to make doubly sure.
Four bidders in total - at £10 £25 £70 £84. I thought it would go around the £70 mark, but as I was determined to have it (My Uncle was flying the plane that won the race) I simply set a snipe for double the most likely price e.g. £140.
Most items are not that rare and I normally set a relatively sane maximum. Tonight, a late 19940s Leica catalogue came up. I set AS to $15. It went above that figure and though it was rare, I am certain another will turn up.
It is a trade off between rarity, your desire for the good and your pocket! If you must have these items, then set a Snipe at double what you think the item will go for ($101.78 say) and make a manual bid, rather than rely on AS.
If it is something you think will appear again, then just bid a sensible amount $52? (If thats around the figure the last ones went for)
Paul