There is simply a point where the average woman will start to have trouble taking it without preperation of some kind.
Just shoved in like a plumber at his first plumbing job most will hate 6 inch girth I assume.
Tendency is that older experienced woman will take girth easier. This doesnt have to be about their stretchability/loosenes but also about their knowledge to handle it.
I can totally see a 16 year old clamping his dick to a size that he isnt able to use and wont fit the love of his life destroying a possible future together.
Its physicly possible for most woman to take 6 inch girth into her pussy if done right and probably on a daily basis for most if YOU know what you are doing.
Im not at that size most the time but I can gauge how some are absolutely wet aroused and tightly stretched to their max at 5.3 - 5.8 needing extended care good timing and slow millimeter by millimeter insertion. 1 step back 2 steps in.
They might have problems taking more and the sex quality would go down considerably if I had 6 inch behind the head girth.
Then there are some who need more and some who could take more easily.
I label myself experienced so I rarely get bad stuff happening and know how to handle a girl that might turn to anxiety.
I had girls tell me they are sore in a bad way next day at 5.5 despite enough wetness.
If you have a wife or GF you want to stay with, just never go bigger then she will like on a daily basis or it could be a relationship killer and you will be left wanking your girth ;)
Now Me myself I aim for tapered dick and am avoiding my girth below the head to get bigger then 5.5 but totally go for bigger then 6 towards the base.
I know how to push the buttons to get the girl taking more then it appeared 10 minutes ago and let her feel safe and it turns to awesome sex and Im very confident I will be able to do that at 6.5 base(!) girth too.
I wouldnt like to go out for one night stands with 6.5 inch girth right behind the head. Lots of turned down getting buyers remorse Im sure.
But hey if your partner will be with you forever and she can take 8 inches girth(possible..) then go for it!
And for length everything above somewhere like 7.5 you have to take outmost care with most pussy as you cant just bang away.
Then again if you are much more then 8 you can also go for 12 as you wont be able to put it all in with most woman above 8 and have to take care anyway..
I dont want to get any longer then I am cause anything more will lead to me having to alter my sex style to the worse! It would be fun for me wanking it but bad with more then 50% of woman I met.
Anal sex: Most wont do anything above 5 if they are not totally into it and do it reguarly.
Blowjobs: Again, a tapered dick works very good as in having a smaller girth behind the head but at 5.5 midgirth sot will have trouble physicly.
So yes 7.5 x 5.5 is probably the maximum most should aim for.