I fitted an oversized hand in a Model 28. It would not carry up well on 4 of the 6 chambers when cocked slowly. There are several threads on this forum that deal with fitting one and I read them all and then bit the bullet and gave it a try.
Generally, don't touch the frame. Do all the work on the hand. If you botch the job, you can always buy another oversize hand. You cannot easily buy another frame. So if you need to touch something with a file, touch the hand.
As I recall, I had to file the hand to first fit the frame window. Then I had to disassemble and reassemble the gun taking just a few swipes across the top part of the hand that engages the cylinder teeth so that the gun would cock without resistance in both single and double action.
It took longer than I thought, ending up being a project I had to do over several days instead of just hours and I left the gun and it's parts in a big tupperware container in my safe between work sessions.
But when finished, my Model 28 had the action I wanted and it still has it. It is delightfully pre-timed on all 6 chambers now and is sweet in either single or double action. Go slow. Work on the hand, not the frame. At least, that's what I did. I am no expert, nor do I play one on T.V., so there's no real reason for me to even post except I did this once.
I am sure there is as much chance of you finding a gunsmith in Northern Sweden more qualified than you to do the work as there was of me finding one here in Central Mexico who could do the work. However, since the time I did this, my gunsmith in Queretaro has done amazing work on timing revolvers and I am sure that he could now install an oversize hand with complete competence. At the time, however, I felt it was probably best to do it myself.
And remember: you can always get another hand. It cannot be any harder for you to get gun parts in Sweden than it is for me here in Mexico and we both know it can be done if one is determined to do it. Anyway, that's my advice on the matter. Oh, and at the very end, the difference between "not quite right" and "sweet" seems to be little more than a file stroke so when you're close, slow down even more and work carefully.
Good luck. Go slow.