I'm thinking of putting together a road bike with an upright position that is easier on the neck, back, and groin. (something along the lines of VO Portuer or Nitto Promenade handlebars). I've seen setups like this on a Surly Steamroller, which has fairly aggressive road geometry. My intuition is that most road frames, intended for a more aero position will not be ideal, but I'm not sure, so I'm asking. Is a different geometry ideal, or should I just build on a road frame?

Some thoughts:

It seems that upright position will transfer weight to the rear wheel, so a longer chainstay/wheelbase will be ideal to balance things out. Therefore I've been looking at some touring frames. But these are overkill for the kind of riding I'm doing (short commutes withouth much to carry).

(Note: I'm also wanting CroMo, horiz top tube, and horiz dropouts)

get an old mtb frame and build on that, that will make it easy to find what you're looking for and mtb geometry by design tends to be more upright.

How about just buying a road bike and putting a tall, shortish stem on it?

In my area there are tons of older steel Schwinns for cheap. The Traveler, Collegiate, etc, should prove exactly what you are looking for. Relaxed geometry, long chainstay, and steel frame should make a pretty comfy ride. Most also came with standard brazeons.

An upright seat position transfers more weight to the rear, but also transfers weight to your groin. So along with a longer wheelbase, you'll need a bigger seat.

You should be able to build most road frames so that the bars are level with the seat, or at least close enough. The wheelbase isn't a concern when it comes to weight distribution. Touring frames' longer chainstays help with stability when loaded, yes, but they also move panniers farther away to eliminate heel strike.

Then there's the other extreme -- going a lot lower for more comfort. There was another BF'er who, after consulting with his shop, eventually dropped his bars pretty low after trying to raise them in search of a comfortable position. What he noticed was that his core muscles started carrying the weight of his torso, reducing the weight felt by his arms. It also took the load off of his shoulders, so his upper back and neck weren't drooping between his shoulders -- which also reduced the pain he was feeling in his neck.

Go look at the RANS crank-forward bikes. They are what you're asking for.
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Thanks for all the suggestions. After looking around, the Rivendell bikes seem to be designed with this in mind: road riding in a comfortable, upright-ish position. They have long chainstays and shallow seat tube angles. The low bottom bracket is appealing too.

Are there any other builders taking a similar approach to their designs?

If not, it seems vintage may be the only affordable way to go (e.g. older Schwinns).

A high number of touring bikes have a more upright position.

A touring bicycle would be a good place to start.

I recently put a Nitto Technomic stem on my C'dale tourer. My handlebars are now practically level with my seat - and I run gobs of seatpost.

My concern with a touring bike is that the tubing diameter and thickness will be much more than I need for my unloaded, usually paved, relatively short rides... but maybe that's not really a big deal.