As I haven't been able to find any information on stem length in the forum, I'm hoping to solicit some advice on a purchase. My girlfriend and I have a mid-90's Trek T200, whose ergonomics are a bit too racy for me. Getting the handlebars at or above saddle height would be a great start. I've had a shim fabricated to enable using a 1" quill stem in the obscure 1-1/4" threaded steerer tube. I am trying to decide between a Nitto Periscopa and a Nitto Technomic. The Technomic comes in 8/9/10cm extensions. I think any of these four could get the bars in a more comfortable position.
My concern is that the short, high rise of the Periscopa would drastically alter the bike's handling. Making a similar change to my touring bike resulted in a very wobbly steering experience with a lightly loaded front rack. While we will probably not have any weight on the front of the tandem most of the time, it would be nice to keep the option open.
Also, I understand that the handling characteristics of a tandem are much different than a solo bike's, but I don't grasp the differences, so this is where I would like advice.
BTW, the current stem is about 12cm, and runs roughly parallel to the ground.