Well, I did it.
17 miles into Devon, down to Tavistock and back home.
I carried a pair of Yellow pages in the front panniers, and had three more YPs in Trailer's box as well as one gallon of water (10lbs) in a big bottle. This weight gave me some idea of towing and carrying.
Me and Chopper did very well indeed! I'd ridden this same route a couple of weeks ago, and had the information in my Garmin Edge 705. I could do the route again and compare the figures and my performance.
Here's a map of where I went:
And here's a profile of the route:
(Red is heart rate and the green is speed)
There was 1800ft of climbing and I consumed a couple of thousand calories. I was tired when I got back! The trouble with Devon and Cornwall for cycling, the hills are constant and regular and we don't have any flat bits at all.
Comparing the same route with before, I was six minutes behind schedule at the top of the hills near Brentor. The last time, I had no luggage and no extra weight, this time I was pulling and carrying, and by the time I made it down to Tavistock, I was six minutes ahead! I can only suggest that going downhill is far more efficient with a heavy weight than being light. Yes, I was slow up the hills, but this was more than compensated by the extra weight pushing me down.
By the time I made it home, I was four minutes ahead of my previous time.
I was tired and my thighs ached, but I was elated and confident. I'll be out again in a couple of days, and I'll try to up the distance.
Practice makes perfect.