TT Tank is great, cant say I notice any weight or balance differences at all really and, now that's it's all plumbed in it's easy to take on and off if you want to revert to "slimline mode" for whatever reason!
Interested in the Hyperpro shock myself - did you buy one "off the shelf" from a reseller over here or direct from Bas? Fed up with the constant adjustment of the air shock, I can never really find the sweet spot and don't even talk to me about how saggy-arsed it was on that trip with all the luggage on! The shock is right up the top of my "to-do" list now and I'd love to get over to see Bas and have the front (already got Hyperpro springs up front) and back suspension looked at together but, with a new baby 3 months away, I don't think I'll manage a trip over to the Netherlands anytime soon, so I'd be looking at buying and fitting myself. That doesn't phase me too much, it's more the setup that seems to be a bit of a black art!