FWIW, I reckon it took me about 5-8 mins longer (over 8 miles) than I’d expect the trip to in daylight (and about 10-20 mins less than trying to do it with crap lights)

I suspect that the noise a dynamo makes is psychologically important – if it’s noisy it certainly sounds like it’s slowing you down. This could possibly make you push harder on the pedals but less efficiently (i.e. pushing straight down at the bottom of the stroke).

There’s a quite different appearance of speed when cycling in the dark too, as you see things close-up reasonably well in the front light, but more distant objects are unlit. Also there’s less to look at, so you pay more attention to the effort of your legs. Possibly.

Every now and then I try easing off my effort on the pedals, and concentrating on pushing in circles instead of up-and-down, aiming to do less work without losing any speed. Often I find I can ease off without any speed reduction, proving that I was pushing too hard!

No, you need less weight, do without the brakes, you’ll be alright.
John

There’s was a very good test of dynamos by Chris Juden a few years back (online here). It shows the amount of drag actually created by a wide range of dynamos. Not one of those tested had as much effect on the rider as a 1:300 hill and there was “quite a cluster of sidewall and hub-driven models around the 1/500 line”.

I’ve had both hub and bottle dynamos, and the difference between them is one of those swings and roundabouts issues. Hubs are usually a little more efficient at night time when the lights are on, but they’re also heavier, more annoying to retrofit, and less efficient in the daytime when the lights are off. I do more riding in the day-time than the night-time, so I normally use bottle dynamos.

The larger idler that chestercycling mentions does decrease the drag a little, but personally I find this difference to be nothing to write home about. I’m currently using one of the smaller idlers on my bike.