Rings, monoblock ... pressing optics to them?

Not quite sure what you mean by "kicking like a horse" but to those of us who have fired large caliber powder burners and ended up with the bruises and flinches to prove it, may I remind you that we're only talking about a .22 caliber air gun. I used to shoot NRA competition with a .41 mag Contender which eventually blew the heads off of the mount screws and threw the scope back into my face gashing my eye orbit, chipping the bone and left me bleeding like a stuck pig. That being said ... yes ... the Hatsan 125 will destroy your scope unless you put it on right.

​I had the "Sniper" version and it had removable recoil pads on the stock so you could get the length of your pull right without having to "crush" the gun against your shoulder trying to get the proper eye relief for the scope.

​I used two piece mounts on mine with a recoil bar running under each mount so it could lock into the picatinny rail on the gun. I was able to get the mounts far enough forward to put the heel support on but with only one screw in it so I put lock tight on it and screwed it down to the point where I was sure that if I tightened it any further it would strip the screw out and butted the rear mount against the heel stop.

Most rings come with some sort of adhesive inside them to help secure the scope tube to the rings, if yours doesn't then you might be able to check out a gun shop to try and find some adhesive strips to put inside the rings.

​Just a word of advice here. Scopes are extremely easy to destroy with a hex wrench while tightening the rings. It isn't hard at all to put too much tork on the ring screws and totally destroy the insides of the scope. Never tighten the ring screws any tighter than you can get them using the small end of the hex wrench ... in other words ... don't flip that hex wrench around and start tightening rings with the long end of the wrench ... tighten only with the short end. It only takes a small dent in the tube to make that expensive scope totally worthless. Make sure that the scope you are using is "air gun rated" or it wont stand a "bat's chance in Hades" with the double recoil of the Hatsan. It's not that it kicks hard, it's that it kicks both ways.

​Hope this helps and I hope that you can get some good accuracy from the gun. 

I would try using the heel first and if you find that you can't get the comfort and accuracy out of the gun that you want I would remove the heel and just go with the monoblock. I was thinking that the only use for the heel was in the case that you sheared the stop pin off on the monoblock. But the truth is that you can make that monoblock a lot stronger than any two piece mounts because you can tighten it a lot more than you ever could any two piece mounts. If you decide to not use the heel make sure that the stop pin is engaged very well in that picatinny rail.

Hope it works out for you