I did my local 300, a tough one with ~2400m listed on the rwgps but ~2900m recorded by two of us, one garmin and one wahoo. I was aiming for 12h ride time, 14h total. Finished in 13:48, with 2h stop time. It was cold at the start, 2C but it was up to 14C by 10am so most of the ride was done in summer kit, with some 3/4 length non-insulated bibs to keep the knees covered. Winds were mild for the first 100km, then it was mostly tailwind for the rest, only ~30km of headwind. I wore my shakedry at the start, along with oversocks and some light overmitts that block the wind well. Warm enough for a couple hours and pack down very small.
I tried drinking my carbs for this ride, brought
960g 720g of sugar with to give me 60g/hr. I mixed 180g with a bit of sodium citrate, into ziplocs, refilled a bottle at each control (~75km apart, perfect). I felt great the whole ride, didn't eat too much extra food, just a few cans of pop, and some chips. Had a couple buns and fruit at the last control but felt like that was too much food. Finished the ride and wasn't ravenous. This morning I feel much less drained and sore than I did after my difficult 200 a couple weeks ago. I think this approach is going to work for me, and it's really cheap too.
This was my first brevet using my new 50mm carbon rims, with 30/32mm gp5000 setup tubeless. I have a road bike with the same tires in 28mm on shallow aluminum wheels and they are fantastic. I didn't put a dynamo hub in these, so that probably gets me 10w into forward motion instead of light. I feel like it's worth it. My old 650b wheels had an SP dynamo and gravelkings, so it's not a fair comparison at all.
I bought a magene radar and it was great to have. Traffic was bonkers since it was the first nice spring day we've had. No false negatives, it did alert a few times to cross-traffic or a bird, or something, but I had no surprises. Really nice to have the beeps when it was windy. I still check my mirror and do shoulder checks, but I like having it. The battery lasted for the entire ride, so it should be good for a 400 with a bit of charging, or I think it'll work while charging, either way I'll find out next week. For 130$ it's nice to have. The garmin varia is 345$ here and doesn't have as good battery life. I don't use the light on the magene since I already have a pile of good rear lights but it's a nice backup light. The supplied mount with the magene would work on most seatstays but with my dropped stays it points too far up. It did attach securely to the saddle though,
I hate hate hate the selle anatomica rubber saddle I bought. It's absolutely one of the worst saddle I've used. It squeaks and makes weird popping noises. I'm also ~10lbs over the weight limit so maybe that's the problem, I somehow missed the obvious warning on their website. It doesn't give me saddle sores but that's the only good thing about. I think I'm going back to my old one, just need to figure out how to attach my bigger saddle bag to a normal saddle.
Also, that top tube thing is a mockup, I came across the apidura race bolt-on model, since I don't want straps. It's waterproof, but has a magnetic clasp instead. I cut up a small jug to see if the general shape and opening/closing would work for me and I loved it... easy to open one-handed, just enough room for my dog repellent, a powerpack, a couple of cables, and gum/toothbrush. The apidura one has a cable port as well, seems to do most of what I want, and what I miss not using a handlebar bag. I have a dill pickle bag so it's not really big enough to stuff a lot of clothes in, and I've found I'd rather just stop to change than trying to to faff around while riding. I'm getting close to being completely satisfied with my setup, though I think a shorter stem with a bit more rise might be better for my hands.