Hi Jane!
If it helps as another data point, most of my bikes are sized and setup in such way that I use stems with 80mm of forward reach. All allow me to have my preferred 45° back angle with slightly bent elbows when riding with my hands atop the brake hoods with drop 'bars, and the 'bar tops are even in height with the saddle top. I am now running a 60mm inverted uplift stem on my 590M Nomad Mk2. Why? The shortest top tube is the "Medium", a bit long for drop 'bars without adjustments, so....
With the short stem, compact reach/drop handlebars, and the brake levers placed so the blade ends are level with the bottom of the flat portion of the drops, I am in the same position as before (deep anatomic drops, 90mm stem, and brake levers set very high on the 'bars) and the bike feels the same 'cos my hands are in the same place as before, even though the stem itself is shorter. It matches the position I have on my other bikes.
In general, if everything else remains the same, a shorter stem with a longer top tube means more of the rider's mass is kept within the wheelbase of the bike, so the front wheel has a bit less weighting. Andy is right; the bike will feel more stable with less-sporty/twitchy handling. Also, because of the longer front-center (distance between BB and front wheel and head tube due to the longer top tube), the bike will be less stiff (mostly laterally, but vertically to a degree) due to longer tube spans. Overall, the ride should be workable.
As for steering
leverage, that is best measured as a vector between hand position on the 'bars and the steerer's axis at hand level -- that is the effective moment-arm, regardless of stem length or 'bar type. This usually causes a flurry of protest among those who first hear it, but one can't argue with physics regarding leverage. Ah, but comfort and the need to accommodate individual physiognomy are different matters, and that's where handlebar width and hand orientation are a matter of individual preference. Same for reach to the 'bars, 'bar height, and back angle.
To that end, I have even had success fitting a
50mm negative stem (short stem,
reversed so it extended
rearward) with exceptionally wide drops for a barrel-chested, short-armed individual who very much wanted drops but found their forward throw exceeded his reach when he finally found the desired width. It all worked beautifully in the end and handling was unaffected because his final position was where it would have been had be been able to find short-reach 'bars in his required width. His leverage remained the same as well, and the bike didn't know the difference in terms of handling. The only quirk was the 'bars rotated 'round in an odd path at full lock when the bike was parked, but it was never a problem in practice.
Jane, I spent a lot of time with my Nomad setup to get things right in 3-D space along X, Y, and Z axes. You're absolutely correct; the 'bars move rearward as they rise. I was fortunate in already knowing how far rearward I need the saddle in relation to the BB, and I wanted the 'bar-tops at the same height as my saddle. Once the 'bars were in that plane, then it was a matter of mix-matching components till I got my hands in the preferred place ("reach") to give my back the 45° angle with slightly bent elbows I also wanted when riding the brake hoods with drop handlebars.
The articles at the following links might prove helpful honing in on what you want in terms of fit, either with adjustments to the present frame or in swapping to another size:
Choosing a frame size*:
http://www.rivbike.com/kb_results.asp?ID=41Fit, sizing, position:
http://www.rivbike.com/kb_results.asp?ID=38Common setup mistakes:
http://www.rivbike.com/kb_results.asp?ID=40Lesson in positioning:
http://lovelybike.blogspot.com/2011/06/back-and-forth-lessons-in-positioning.htmlThe top tube ruse:
www.rivbike.com/v/vspfiles/assets/images/ttr_excerpt.pdfDetermining correct size for touring bike:
http://biketouringnews.com/what-size-touring-bike/right-size-touring-bike/Finally, if you or others are considering drop handlebars, the following article is a useful read; it compares the myriad available bends and resultant reaches:
http://ruedatropical.com/2009/03/road-drop-bar-geometry/*Keep in mind (wrt the Rivendell links), Grant Petersen doesn't mind toe clip-front wheel overlap. I do. Andy Blance also avoids it by design.
Jane, I feel your understandable frustration and angst and am hoping something in the above might prove helpful to you achieving a good fit, either with this frame or the next.
Best,
Dan. (...who thinks "Fit-ness" would be a good term for bike sizing)
