In all seriousness, John,
http://fnrttc.blogspot.com/p/its-most-definitely-about-bike.html is worth a read.
It's not a long ride, but it can feel a lot longer if you're hauling stuff along. I generally do a bit of wayfinding immediately before the halfway stop, having let the front of the ride off the leash for the last few miles. I see people coming in at the back of the ride panting, and that's often because they're bike is unbalanced by luggage and they've got too much bulky clothing on. If you're at all worried then strip everything off that you don't need - your bike will run more freely, you'll feel a good deal fresher, and you'll save your breath for the stuff that FNRttCers do best - chatting.
It's not the set-piece hills that will do you in - walking those is no disgrace - it's the long drags up through Sutton and Crawley Down, and the seemingly endless road in to Ditchling which has a rise of about 150 feet in a tad over 3 miles. That's when you need the bike to respond to a bit of pressure going up any slight stiffening of gradient.
Nobody ever starved to death on our rides. Leave the cake at home. Bring some energy drink, but dump the pannier and rack, and burn the mudguards (which have caused at least one half hour delay to the entire ride...). I let McW get away with all that clobber because he's pretty damn speedy.
Many of us manage with lightweight layers on our top halves that can be stripped off and put in a back pocket. If it's a dry night then don't wear a bulky anorak.
The trick is to not think of it as a bike ride at all. It's a fun night out on wheels. Ian's quite right in saying that you won't hold anybody up, but part of the joy of a night ride is the sense of freedom that comes from empty roads, and the friendships that spring up as you wheel along without a care in the world.