FW, if you like them that big, you might consider fisting as your next great adventure. I hear some women are really into that. I've never tried it. Seriously though, some women are really into it. You might want to research it.
So, again, this would be tricky to answer. If I was single, yes I'd probably go for a 7 or 7.5 inches. But, since my wife would not like it, I probably wouldn't consider it at this point in my life.
I honestly don't understand fisting. I don't get it, have no curiosity about it, and wouldn't do it.
Remember in a previous post I said I was with a man who claimed he was 8 inches but I'd guess he was probably 7.5. And it was HUGE, from my perspective. I could not even get it all in. I would have had to work with it over time and have long sex sessions in order to actually take it all. We never got that chance, but I know I could have gotten there.
THAT is as far as I would ever want to go regarding having something (from my perspective) HUGE inside of me....and it would take work and effort. (Course the work and effort would be by having sex so, for me, win win!)
I love just getting fingered. I mean I LOVE it. I could do just that for an hour (with the right skilled hands). I'm usually most comfortable with just one finger. Two seems to add weird angles and knuckles or something and just isn't comfortable to me.
A fist and arm (especially a man's!) would be so much bigger than the pleasantly thick 7.5 inches I said would be ideal for a penis! I would never even fantasize about a freaking arm inside of me. Yuck.
But I do understand, you were being helpful....and not only that, apparently lots of women are into this. I don't get it, but they do so, it's all good.