A little quirk of the extra wheel trailer for those who don't know is that there can be problems with "low" mudguard stays.
My Gilles Berthoud stays had to be raised to allow a decent amount of trailer up and down articulation.
Without moving the mudguard stays upwards, the trailer was forever hitting them.
You can see the original holes in the fenders and how much I raised them here:
With the resulting 13 inches of upward articulation
My Extrawheel trailer wheel is a mirror of my Ogres front wheel in that it shares its Velocity Dyad rim, CX-ray stainless spokes and Son28 dynohub with E-werk charging system.
Hard to tell from the last pic due to the angles and photo compression, but all the wheels are the same size as are the tires (2.00x622).
Only done a short tour on it so far but very happy with it.
Will be doing an extended tour (over a month) with it after the Easter holiday season when campground prices are lower.