If you look at the Alliant website http://www.alliantpowder.com/reloade...aspx?gtypeid=1
you will see that they list a max charge of 8.6 grains of Power Pistol for 976 fps with a 200 grain Speer bullet in the .44 Special, and 15.5 grains for 1573 fps with a different 200 grain Speer bullet in the .44 Magnum.
So, you should be able to find a charge weight somewhere in the middle of that span that will give you 1100 fps in a .44 Magnum.
Of course, the velocity in YOUR gun will be a little different from somebody else's gun, so if you want EXACTLY 1100 fps from your gun, you will need to chronograph your loads.
If you don't really want to go to that trouble, you can probably get a reasonable estimate from QuickLOAD. Just using a 4" barrel and the default parameters for the .44 Magnum and the Nosler 200 grain bullet in QuickLOAD, my guess would be somewhere in the vicinity of 11 to 12 grains would give you 1100 fps. Somebody here could run a more detailed calculation for you if you want to go to the trouble of measuring the water capacity of a case fired in your gun. But, QuickLOAD is not all that accurate for revolvers, so I don't thing that is worth your trouble.
Anyway 11 and 12 grains are less than the 10% reduction for a "start" charge for the .44 Magnum, so there is no need to "work-up to those loads. And, the same powder/ bullet combination is used at much lower pressure in the .44 Special, so you don't need to worry about it being a squib load, either.
I suggest that you shoot a series of loads varying from about 10 to 13 grains in increments of maybe 0.5 grains and see what is the most accurate, then just shoot that, no matter what velocity it is giving you.