Mark, the Mini was originally designed without an optic in mind. It ejected more up than to the side.
The redesign (Ranch rifle) changed the ejector so it now ejects more to the side, but some guys still have brass hitting their optic.
Putting the scope or dot on the Ultimak eliminates that problem.
Sometimes the rear sight is in the way when scopes are mounted over the action, so the owners just remove the rear sight., not a good idea.
Having nothing over the action makes it easier to clean, and remove the bolt.
I find balance is improved and the carry point is unobstructed with a forward mounted optic.
Scopes mounted over the action necessarily have to be high, to clear the rear sight and flying brass. Nothing is more awkward than a too high ( or too big ) scope on a Mini.
A Mini's stock has some drop to it, because the sights are mounted nice and low. You want to mount the optic so there is a similar cheek weld on the stock.
Mounted over the action, there is only a "chin weld". It feels awkward, and is slower to get into action.
When I put the Mini up to my shoulder, I'm looking right through the middle of the scope or dot.
With an optic mounted over the action, when you mount the carbine you have to take another second to scoot your head up a bit to be able to see through the center of the scope. That's why many guys have to use a strap on cheek riser. If and when they go back to using the irons, they have to take the riser off.
Nothing gets the optic lower than the Ultimak:
Just like an Accustrut, the Ultimak helps accuracy by further stiffening the barrel, and acts as a heat sink to disperse barrel heat. And no, they don't even get warm on the outside when shooting. Maybe if you did 10 or 20 mag dumps in a row.
Older Mini-30's have never had the vertical stringing or heat issues that plagued older Mini-14's as they've always had a thicker .625" diameter barrel, so the 30's aren't helped much by a strut. I do have a strut (short one clamp Socom model) on my wood stocked Mini, but it is more for the M1A gas system look.
My other Mini that has an Ultimak and no strut, but it is just as accurate as the other one.
The best thing by far though, with a forward mounted optic, is greatly increased peripheral vision.
Having an optic right up against your eye, and with one eye closed no less, is about as tunnel vision as you can get.
With that scope or dot mounted close to a foot away, you can see additional adversaries, or maybe that much bigger buck off to the side, that you'd miss with a scope or dot right up against your eye.
A T.V. screen dot like the FastFire III I use, is even better than a tube style red dot for downrange awareness.
For sling mounting, the side mounted sling has numerous advantages. A bottom mounted sling, like the factory provides, is good for casually carrying the carbine, but that's about it. If you want to sling the Mini across your back and have both hands free to do other tasks, that 20 (or 30) round magazine will be digging into your back.
And having the Mini slung on your shoulder is not very quick to get into action, like the front carry.
With a side mounted sling, you can use the sling around your arm as a shooting aid, or carry over your shoulder, but you have much better carry options.
Carried in front, all you have to do is raise it up:
Every soldier and Marine in the U.S. military carries the same way:
I started out putting a Q.D. sling socket on one side ( the right side for me cause I'm a lefty), and a short piece of rail on the other for a flash light.
I used a Noveske flush mount shown here on a Hogue stock:
Or a Magpul one:
That set up is O.K., but I now just put the short rail on both sides. If a right handed friend, or my daughter visiting wants to use one of my Mini's for the day, I just switch the sling over to the other rail, using a swivel mount that clamps onto the rail.
This Magpul one is a bit more expensive, but is Melonite coated steel, and has a dual button to prevent accidental release. (I've never had an accidental release with the single button ones though):
The Magpul polymer rails are plenty strong, and lighter and half the price of their aluminum ones.
They come with little T-Nuts, they have to be slightly countersunk to clear the heat shield inside the stock.
On a synthetic stock, there is just enough room for the flat part of the nut to clear the heat shield.
Here the nuts are on a Choate pistol grip stock, heat shield is not put back in yet:
One last thing, if you mounted the rear swivel on the side of the stock, the carbine tends to want to roll away from you. Mounting the rear swivel at the top of the stock greatly reduces that:
On the synthetic stock shown above, you just remove the butt pad, and can reach inside the hollow stock to secure the T-nuts. On a wood stock you'd just drill a hole for the swivel screw.
For guys that have the old style Ruger wood stock, you can mount the swivel without drilling a new hole, just take out the top buttplate screw and replace with the swivel, same coarse wood screw thread:
As far as slings, my favorite is the Vickers Blue Force Gear, I have them on all my AR's and Mini's.
I have a thread on perfectunion's Mini section called "Sling Mounting Options for the Mini" for more reading on the subject.