I am 5.875" minimum circumference not pumped. I have a 2.25" and a 2.5" tube. I can use both comfortably, but preferr the 2.5. The 2.25 can feel a little restrictive around the base. I noticed I get length gains using the tighter tube and girth gains with the wider tube.
My regime is warm up in the bidet for 5 minutes with stretching then pump to 7"hg hold for 1 minute repeat 10 times.
For extra girth do a further session to 11"hg hold for 1 minute, repeat 5 times.
Pre-pump flacid girth behind head is 5"
Post-pump flacid girth behind head is 6" after first session and 6.5" after second session.
Flacid girth behind head after 24 hours 5.25".
Hope that helps