Nginx Ability to limit a force SSL address

I'm working on a forum that was previously vBulletin, and has been migrated to XenForo.
It has a number of paypal subscriptions, and I've got the PHP scripts to do the work...but I changed from /forums/ to root (forcing www).

Checking paypal IPN, it's following http://domain.com/forums/payment_gateway.php?method=paypal

So I need to remove and force a non-www, not secure single item.

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Is that possible within the nginx configuration? I originally followed your force WWW setup.

 

The IPN is inside of Paypal, I don't see a way to change the IPN for paypal.

 

Guess that's what's confusing. Yes you can update the future IPN url, but previous subscriptions you can change? Surely it's not that simple, as no one on XenForo has said it was for migration of paid subscriptions.

 

I did update the IPN, but it's not working properly.