I used to have better than a 1/4" smaller base than middle.
But through base squeezes and pumping, I now have the same size.
There is probably another name for the following technique, but I call it a "base squeeze". For a base squeeze, you need to be a little erect, at least a #2 on Alternative measure of erection level.
Grip with an overhand "OK" grip with your off hand around your base. Try to get as close to your pubic bone as possible. I’ll call this the base grip.
With the dominate hand, use an overhand "OK" grip and grab around the middle of your unit. This is the top grip.
Then kegel two or three times to get some new blood into the area. Tighten the base grip firmly and kegel one time more. Keep the base grip tight.
With the top grip, squeeze lightly and push the blood back towards the base, starting at the head. Once you get to the middle of the penis, tighten up your top grip a bit and push the blood back towards your still tight base grip. Do a reverse jelq towards the base several times until the area between your middle and base becomes engorged. Then really tighten your top grip and push all of the blood in this area towards the base. I call this the "contraction". Hold this for thirty seconds and let go of the top grip while trying to hold constant the base grip tightly. Try to prevent blood loss from your bottom grip. After contracting for 30 seconds, relieve the top grip for 5-10 seconds.
Repeat the procedure by working the blood back down from under your head toward the base with the slight top grip riding down along the shaft. Once you get to the middle of the penis, again, tighten up your top grip a bit and push the blood back towards your still tight base grip. Do the reverse jelq towards the base several times until the area between your middle and base becomes engorged once again. Then do the squeeze with your top grip, pushing the blood towards your base grip for another 30 seconds.
The key is to always have a constant tight base grip.
I do about 30 of these at a time several times a week.
A variation is to do the exact same exercise, but when you are doing the contraction, bend the area during your 30 seconds.
I have also tried this with a clamp and velcro straps, but found it most successful with the two hand technique. There was too much pressure build up for me with the clamping and strap and my erection level shot through the roof and I didn’t want to injure myself and the vlavles at the base of the penis to hold in the blood supply.
Also, I found when I pumped, the base got larger too. I didn’t do anything special, but just noticed the observation.