I've posted about this before so at the risk of being redundant, I've tried both TechSights and a scope on an SKS.
TechSights are a functional improvement over the standard open sights. Like most any peep sight, they make it easier to see the front post and target, and they extend the sight radius by several inches. For many SKSs, however, they are a permanent modification in that you have to alter the takedown lever for the receiver cover. They also make it slightly more cumbersome to field strip the rifle (not a big deal if it's just a range gun). I use them on two of my SKSs and they do help me hit more consistently, mostly because I find it hard to focus with the standard sights.
The only optic solution I've seen and liked is a PU type scope mount from a Mosin Nagant. The mount fits close to the same place as it would on a MN, side of receiver, and sits high enough to allow use of open sights (although probably not TechSights). It doesn't prevent normal field stripping, and you won't have to worry about losing zero unless you remove the scope/rail (not necessary).
I happened across a rifle that already had the rail, but someone had mounted a cheap set of rings and a scope. That setup didn't work for crap, but I've mounted standard PU type rings and scope (replicas) and they seem to be pretty solid. Stripper clip use is not impeded nor is shell ejection. It also looks more appropriate for that weapon and not like a pig in a dress, IMO, if that matters to you. I have not tried this at the range because it's the setup from my Mosin Nagant and I have far too much fun shooting that to constantly rezero it on my Mosin. The downsides are that it's heavy and can't be found for much cheaper than $250 new for the whole setup, mount/rail/scope.
A similar setup with a side/receiver mounted optic is the only way to go if you want a scope on an SKS, IMHO. Wouldn't have to be the PU type; it's possible to fit a different kind of of rail there. But they almost all will require drilling and tapping plus modification of the stock to fit. Also, most scopes will require a deflection shield over the ejection port.
Here's a shot of the original setup I bought it with (crap).
How it looked with the PU scope.
Not exactly center bore, but not off by nearly as much as some AK scopes, and no higher than the receiver cover mounts I've seen. The PU scope doesn't have much eye relief, but the short LOP on the SKS puts you right about where you need to be. The recoil isn't so much that you'll get poked in the eye.
YMMV.
jm
