I have an Easton EA 70 90MM 15 degree rise stem for sale if you are interested.

Fyi, I didn't think the bit fit poorly, but i didn't ride the size down from it (frame only, not built up). The shop owner was insisting that the 90mm stem wasn't for me though, and was talking about how much more stable the handling would be on the 53 vs the 55 (actual top tube on the 55 was 56). He was saying the longer stem would make it more stable... Anyways, I'm just not sure if he's just trying to sell me the bike or if i really should ride the size down. I ride a 55cm top tube on my current bike (not sure the stem length but i'm guessing it's 100mm) and he thought it was too small...

Listen to the shop owner and try the next size down, what do you have to lose?

Personally, if I'm between, I'll go down a size. A lot of that has to do with my stumpy legs and need for top tube clearance, but that may not matter if you're talking about a sloping TT frame.

Tangential question --

Would you (that is, the collective "you") rather have a shorter bike with a longer stem, or a longer bike with a shorter stem?

I would try the next size down if I could, obviously. Problem is it's a frame only and not built up and he doesn't want to build it up just so I can test ride it.

+1 Wrong size frame = pile up your money and light it on fire.

What bike are you looking at?

Don't they have another 54 in stock that's a similar geometry to the bike you're interested in?

20 years ago, I would always answer with - down a size. I liked the look and feel of a smallish frame.

Now, if I'm on the cusp, I'd go with the larger for handlebar height. I've realized that minimal standover is absolutely OK and - assuming you can get the reach right with at least an 80 or 90 mm stem - the larger frame will likely allow you to have the handlebars higher relative to the seat height. That's more important to me now than the look and sporty feel of the smallish frame.

You can modify stack height and/or angle of the stem to get the necessary height if in between sizes.

I figure it's easier and cheaper to change stems than it is to wish you got a smaller frame if you're in between sizes.