Oh, and if you're looking for a more simple solution, just set your tandem up to match your most comfortable single road bike's position. This can be done alone or more easily with a helper but what you'll want to do is to measure your single bike dimensions for:
1. Seat height: Measure from the center of the crank axle to the top of the saddle along a line parallel with the seat post.
2. Seat Set-back: Drop a plumb bob from the nose on your saddle down to your cranks and measure the distance from the plumb bob's center line (the string it's hanging from) to the center of the crank / bottom bracket axle.
3. Reach to Handlebar: Measure from the nose of your saddle to the center of the handlebars. (NOTE: Using line-of-sight techniques for bike fitting are not reliable, e.g., handlebars block view of hub -- too many variables).
4. Handlebar Height: Measure the distance from the ground to the top of your seat and then from the ground to the top of your handlebars and subtract to find the difference. Remember, you're after the vertical difference between your seat and the handlebars, i.e., how much lower or higher are they relative to your seat. Recreational tandems are normally set up with the handlebars a little bit higher than a single road bike. I think ours are about 3cm higher which is still pretty low compared to most.
5. Handlebar Width: Personal preference here. I used to use handlebars on the tandem that measured one size (44cm) wider than my single bikes (43cm). Over time I've started to fit my single bikes with the wider bars just to keep it consistent but, ultimately, it is normal to have bars that are one size larger on your tandem vs your single bike for added control.
6. Saddle Tilt: Check to make sure the surface your standing on is level with a short mechanic's or carpenter's level. Next, put a flat plate (I use an old license plate) on top of your saddle so that it rests on the high points at the nose and tail and then put your short level on top of the plate. Note the amount of tilt based on the position of the "bubble" in your level. (FWIW: After playing around with saddle tilt for about 10 years I finally realized that zero tilt works best for me).
Apply these measurements and settings to your tandem and you should be fine. Regarding the extra 5mm in the cranks, keep in mind that it's only 5mm, or .5cm or about 3/16". (.19"). That's not a whole lot and considering how much you move around on a saddle as you ride (forward when spinning, back when hammering) so it's not going to throw you off much at all going back and forth between 170mm on a single bike. Therefore, I'd set that factor aside until you resolve the overall fitting issues.