It's a bit of an 'How long is a piece of string?' question isn't it?
To try and answer the question, your candidate trike will have:-
1. A strong rider,
2. A top gear a fair bit 'taller' than 100",
3. A strong rider,
4. A well reclined seat,
5. A strong rider,
6. A fairly narrow set of tyres which will make it slower on really rough roads,
7. A strong rider,
8. A fairing, or part fairing because, once you get over 20mph wind speed, a fairing really makes a difference,
9. A strong rider,
10. A light overall weight,
and finally, did I mention a strong rider?
A Quest would fit the bill. Unfaired recline is going to be even more important as is rider power.
Did I mention a strong rider?
What will be slow is a heavy trike, not properly set up for tracking with a low top gear, some cheap and nasty treaded tyres and an upright seating angle.
The rider will be 60, be overweight and have Asthma, hang on that's me!
