Haha, I see myself in a couple of points here. For context, the bike I went for is an HP Velotechnik Streetmachine GTE, used and in very good condition.
Can't adjust the boom to be short enough so that my GF can try it. So we are talking about renting a semi-recumbent tandem one day to share this experience. A nearby shop used to have a Pino Hase for rent until recently. We're hoping they will soon have one again. I've grown a huge curiosity for semi-recumbent tandems since. It seems to address a lot of small things that our upright tandem isn't perfect at - and it would be nice to experience this alternative concept.
On your notes:
1) If you're lucky you can buy from a bike enthusiast who has already upgraded everything 5 times and kept original components. That gives you lots of spare parts and fancy upgrades!
2) I have suspension and like it a lot, but I live in rolling hills country, not mountains. Still experimenting - tires seem to have a huge influence on bike speed. I am playing around with road bike tires (Schwalbe Durano), which do seem to feel okay given that I have suspension. Uphill is still the same story.
5) Oh yes, I also noted the loose sand & gravel thing right away. Seeing some Azub guys MTB'ing on their bikes is really impressive.
6) It feels a bit like our upright tandem in that regard, which has a similar characteristic. It's so much fun to experience the downhill acceleration (and we just forget about the uphill, once it's done
).
Cheers!