Klaus has answered in German as I don’t have the vocabulary to explain myself, but here are my thoughts in English:
The QuattroVelo is my first ‘new’ Velomobile and I didn’t know there would be a period of ‘running in’ like a car, but I was still shocked at how tough it was for me to ride.
I had a list of important things for Velomobiles and, in random order, this list was:
Comfortable
Luggage Space
Waterproof
Rolls well/fast
Easy to get in and out
Corners well at speed
Handles tight corners acceptably (Wendekreis)
Ease of maintenance
The QV is good at several things where the Milan is not (waterproof, wendekreis, maintenance, luggage space). However, having toured with it I have discovered that these items are actually rather unimportant compared to the real vital items, which are efficiency/speed and comfort. It doesn’t matter if you can carry twice as much luggage if you can only ride half the distance and your arms hurt. I am now touring with the Milan and can fit the luggage in that I need (although it takes a little longer to stow everything away), I can get round the corners on cycle paths if I am careful and most importantly I can sit comfortably for a full day and am able to ride at a decent speed.
We plan to take Humphrey to Dronten to check there isn’t some issue slowing him down (and we are pretty sure the seat is cracked at the bottom where it fixes to the QV) but I suspect the real problem is that I do not have enough power to ride this heavier Velomobile without exhausting myself. That is no fun. Plus getting in and out several times in a day causes muscle pain in my good arm and when sitting in it my arms are squashed uncomfortably by my sides.
We will see if Velomobiel can suspend the Tiller for me, but no changes that they make will widen the cockpit so that will always be an issue.
If I can’t get Humphrey right I will sell him. Paying 9000 Euros for a bike I just use for my 8,4km work commute is ridiculous. I though I would use him for commuting and touring, but it seems touring is out because of the uncomfortable cockpit. I would rather have an electric car for commuting in the rain and it would probably be cheaper!
I am very grateful for all the replies and comments on this thread, it has been very useful to read indeed!