Good to see you at the start, Feanor.
As for the ride, we made a right meal of it. Puncture (thanks to the potholes on the run in to Eskdalemuir) , injested rear-mech near Boreland, and rear disk brake issues at Langholm all contributed to the PITA factor. Mostly, it was about our lack of on-road hilly miles on the tandem.
Although the climbs were never that tough singularly, with the exception of the last run in to Selkirk, the descents weren't so tandem-friendly, being of the itty bitty gritty variety, so it seemed I was always on the brakes.
We got back in time, but the desire to DNF was quite high at times. This was entirely our issue - the route is fantastic, the views breathtaking, and the organisation excellent.
ETA: I guess this is everything an early-season ride is about; ironing out the bugs in the hardware, and the wetware.