Given that he mentioned not being comfortable with his position in the first post, I'd lean towards duplicating the length and letting an increased up angle provide that comfort. With that said, OP, you might want to consider whether it's the weight you're putting on your hands or the length of your reach which is causing the discomfort - these are (subtly) different aspects of fit; you might for instance find that a longer stem that's the same distance below(above) your seat, generating essentially the same pressure on your hands, will solve the problem or you might want the more-vertical seating position of a raised bar, probably not possible without an adjustable stem. It's a somewhat complex and subjective relationship. And keep in mind that stems are offered in 10mm length graduations for a reason. A longer stem at the same angle will effectively raise the bar, and in hindsight I think that Dunbar and I are saying essentially the same thing.

Case in point: I'm really happy with my current riding position, using an adjustable stem. That position, however, uses all the available spacers below the bar, and zero angle on the stem. The "solid" stem I'm replacing with is at a 6/84-degree angle (depending on which way I orient the install), so I'm going to cut my new fork long to begin with and try the new stem both ways (moving spacers above and below the stem as I do so). If either work equally well, I'm going to opt for the "84" configuration to have the stem at the top of the spacers and a "racier" look to the whole thing.

Mind you, I am abnormally anal and world-class neurotic. Chances are your solution will be far simpler than mine.