I have the Chromoplastic mudguards available from SJS. On Raven Tours, not Nomads. Both bikes are currently running 2.0 Marathon Supremes.
On 1 bike, I have the 55 mm version, as delivered by Thorn. On the other I have the 65 mm version from my LBS.
I prefer the 65 mm as there is more mud clearance and more room if I want to fit studded tyres or (slightly) wider tyres later.
The 65 mm version I have features a cut-out near the bottom bracket to allow chain clearance for a derailleur bike. This could allow more mud onto the transmission, but as I have fitted Chaingliders it doesn't bother me. I don't know if all versions of the 65 mm Chromoplastic mudguards have this cut-out, but it would be a factor to consider if running a bare chain. Or maybe use another brand.
Brakes may be another thing to consider, but you can generally use spacers to move the mudguards down a bit to increase clearance between mudguard and brake noodle.