Anything you do to reduce the "barrel whip" of the older pencil barrel Mini's will help.
Even just cutting an inch or two off the factory length will in effect create a stiffer barrel.
After shortening, the muzzle will need a re-crown. Ruger's crowns are mediocre at best, you will see another slight improvement with even a re-crown using hand tools like those available from Brownell's.
Adding some weight on the end like threading for a flash hider will help as well.
Most all Mini's are way overgassed, and reducing that (and using Wilson 1911 buffers on each end of the op-rod will help.
Typical way to determine if that Mini is overgassed is how far the carbine flings brass, 40 to 50 feet is way overgassed.
However, as the 181 series were "pre-Ranch", they have a different method of ejection, and will eject a sane distance of 3 to 5 feet, no matter how the gas flow is changed.
I don't know if I'd shorten one to just ahead of the gas block, though, as you'll then have a tough time getting enough gas to cycle.
The shorter the barrel, the more gas needed.
The new Tactical Mini's with 16" barrels need a gas port bushing at least .020" bigger than the 18" barreled ones.
I shortened a Mini-30 to 16" for my daughter, and it wouldn't even cycle with the same .065" bushings I use in my two longer barrel Mini-30's.
I put the stock .100" one back in, and it now ejects the same distance as my 17" and 18" Mini's, about 14-15 feet.
Velocity loss will be more significant with the 5.56mm by going to a shorter barrel.
In the 7.62 x 39 Mini-30, I've found that I get MORE velocity out of the 16" barreled Mini than my longer ones.
Seems powders in the x39 are optimized for the AK, so the x39 likes short barrels.
If you cut back to just ahead of the gas block, you can find on E-Bay the top half part of the gas block that has a sight blade on it, and I believe Lee Hadaway of The Arms Room, in Trinidad (or is it Pueblo) Colorado makes one as well..
(Other factors would be increased muzzle blast and decreased sight radius, but you are already aware of that with any SBR).
Here are my 3 Mini-30's. The one on the left that I modded for my daughter now has the old style Ruger wood stock with shorter LOP, the Choate PG stock shown was fast to swing and light, but had fitment issues so was replaced.
If you like the Troy stock, it's your gun. But no way would I put a heavy, sharp edged stock like that on a Mini.
I seriously doubt anyone would ever need several feet of rail like a Troy or Sage stock has.
I put a 3 inch section of Magpul polymer rail on each side of the forend, plenty for a sling mount and flash light. Plus I have the Ultimak railed hand guard for an RDS, scope or laser if needed.
The Ultimak has the same barrel stiffening and heat dispersing qualities as a strut, but is also the best place to put an optic, out of the way or the action and rear sight.
If you were going to use a strut, I'd recommend the Accustrut over the Mo-Rod or H-bar.
Kevin was the originator of the strut for a Mini, and his have the cleanest lines and clamps.
But with a barrel that ends just past the gas block, just where are you going to put that Strut ? Won't be enough barrel sticking out for even a one clamp Accustrut Socom . With an Ultimak, you can get the advantages of a strut, and not need 4 or 5 inches of barrel sticking out pas the gas block in order to mount a strut.
The 2 clamp strut (with dimple option) is by far the most effective at helping the old pencil barrel Mini's, but you'd barely have enough room to put one one a 16" barreled Mini, much less one that is 13" or so.
Here is the two clamp Accustrut on an 18" barreled Mini:
And I'd avoid buying anything (except maybe a 3 pack of gas port bushings) from ASI, they charge double, even triple for stuff that you can get elsewhere.