Originally Posted by Reddleman

I’ve managed to stop quite weighty trailer loads using V brakes on a 26” wheeled hybrid bike, so I wouldn’t be too worried about that unless you have a very long descent where smaller wheels and continuous rim braking can apparently cause tyre blowouts according to Moulton owners on other forums.

As it’s a custom built frame, why not get mounts for both options brazed on and save the decisions for later? Add in a set of wheels with rims suitable for braking and hubs that can have a disc mounted to them, and you can upgrade easily at a later date if V brakes aren’t enough for you.