Get a youth model. They usually have shorter stocks and are not any more expensive than a standard model. You can then just add a recoil pad to get the fit just right. I have a Youth model 870 and the receiver is also 20ga sized, so the whole package handles and feels smaller, even though I've added a recoil pad directly to the youth stock to make it fit me. It's a shotgun that handles like a .30 Carbine. It's FAST on target and will bust clays like nobody's business. People think it's an odd gun until they try it out, then they offer to buy it.
Indoors you aren't going to get huge patterns anyway. At those ranges most of the load is going to be pretty close together. Heck, I wouldn't want to get hit with birdshot at hallway distance.
I don't know if Remington makes a Youth 1100, but if they do, that would be the ticket.
Ross