Tulok

After measuring my sister and entering the numbers into a calculator I've got that she needs a 52cm top tube with a 100mm stem for a road bike. The thing is, we want a vintage mtb to put some slicks on. The longest ride we'll ever do is 60 miles, but she just doesn't like drops, but doesn't mind leaning over for an aerodynamic position.
What I'm asking is:
What do you think would put somebody in the position of approximately "the hoods" on a flat bar late 80's mtb?

RobbieTunes

Use a road stem.

Tulok

I guess that makes sense, get the back flatter. I'm thinking a 54-56 top tube, 80-100mm stem, bar ends and go from there.

repechage

I set my mtb. up that way, basically the same drop and reach as when I am on my road bike. (same seat setback too) in doing that the stem got quite long, 140mm minimum rise. Set the saddle and let the bike tell you, in general, it is going to be 25 to 35 mm longer than a road stem. The mtb. has a long top tube but the slack seat angle and associated setback it suggests is not used. On my mtb. I use a zero setback seat post.