Depends what you want.
If you’re into quickies, then your goal size should be smaller than if you’re into marathon foreplay sessions before penetration.
Likewise, if you’re into hooking up with girls only once, then your goal size should be smaller than if you’re into longer-term sexual relationships (many “tighter” women adapt fine with time).
Here are my utterly unscientific suggestions, based on the possible combinations of the aforementioned two dimensions:
1. Prefer quickies, hooking up with girls only once: 7 x 5.5 nbp
2. Prefer quickies, hooking up repeatedly: 7.5 x 5.75 nbp
3. Prefer marathon sessions, hooking up with girls only once: 7.5 x 6 nbp
4. Prefer marathon sessions, hooking up repeatedly: 8.5 x 6.5 nbp
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