I didn't see any threads dealing with this, and it's seems like a stupid question, but I'll ask anyway.

I can't find any illustrations, or simple explenations on how to carry. No matter how I seem to sling it, and it's a Scepter QCB, it seems like the ejection port is going to be blocked. Aside from getting it out to the range, which hasn't happened for the past 3 weeks due to the weather, and trying it, I figured I'd get some feedback beforehand.

I shoot a rifle left handed and have had some problems/concerns with 3 point slings also.
So I have usually used 2 point slings on KAC QD swivels mounted to some combination of the receiver end plate, buttstock, and forward rail.
The slings I have used are usually either modified 3 point (Specter), Bushmaster M-60, or custom made from stuff accumulated over the years.
Thanks to member Bullseye_Doc_Holiday I found out about the Viking Tactics Wide (Padded) Sling with 3 point type features and have to report that while expensive it is excellent for a southpaw.
www.vikingtactics.com/ForSale/WideSling.htm

And to boot, I shoot pistols right handed. So having the rifle drop to the left side is how I naturally want to carry it.

Quoted: And to boot, I shoot pistols right handed. So having the rifle drop to the left side is how I naturally want to carry it.

Same here, righty pistol, lefty rifle.  It's actually pretty convenient, and with a "patrol" carry sling setup, you can actually bring either weapon into action quickly, or both (if you need to cover two  different lanes, say 90 degrees to each other-think hallways, at once).

I designed a southpaw friendly tactical sling.
I have some second gen prototypes going out next week to some local swat, auto crimes and narcotics task force guys I worked with before my injury. This one is pretty unique, the feedback so far has been outstanding. First production units should be going out next month. e-mail me if you are interested.

The design allows you to:
Shoot strong or weak side without removing and re-mounting weapon.
Allows you to climb ladders, negotiate obstacles, fastrope etc. without removing and re-mounting weapon.
Completely ambidexterous.
Convertible to one point in under two seconds with no worry of losing extra parts in the field.
Quick disconnect on non firing hand side.
Quick adjust on non firing hand side.

I served 12 years LEO and 3 military counterterrorism unit before I got hurt (spinal cord). I never found the exact sling I wanted. Mainly being able to go from firing position to being able to climb a tactical ladder and back to firing position immediately, without re-mounting the weapon. When I got hurt I designed it, now I am making it...

Well made, by hand, by me.
When I put the website up next month I am thinking of posting video of this thing towing a car...

[email protected]

Quoted: I designed a southpaw friendly tactical sling. I have some second gen prototypes going out next week to some local swat, auto crimes and narcotics task force guys I worked with before my injury. This one is pretty unique, the feedback so far has been outstanding. First production units should be going out next month. e-mail me if you are interested. The design allows you to: Shoot strong or weak side without removing and re-mounting weapon. Allows you to climb ladders, negotiate obstacles, fastrope etc. without removing and re-mounting weapon. Completely ambidexterous. Convertible to one point in under two seconds with no worry of losing extra parts in the field. Quick disconnect on non firing hand side. Quick adjust on non firing hand side. I served 12 years LEO and 3 military counterterrorism unit before I got hurt (spinal cord). I never found the exact sling I wanted. Mainly being able to go from firing position to being able to climb a tactical ladder and back to firing position immediately, without re-mounting the weapon. When I got hurt I designed it, now I am making it... Well made, by hand, by me. When I put the website up next month I am thinking of posting video of this thing towing a car... [email protected]

Tomorrow will be the first time in a month that the weather will coencide with my schedule for going shooting. I'll finally try the Specter sling, with what looks to be a strap blocking the ejection port. If it's a pain in the ass, I'll be looking for something different.