Clipping with one of DCG's plugins is what I meant since there is no native clipping abiity in Carrara. 

HDRI: the camera simply needs to be set as Spherical and at the 'eye' level you want the horizon line to be when used as a spherical background - for outdoor 0,0,0 is good, indoor will probably be the height of the camera if you were standing. The reason many free HDRI and spherical background look bad is because they are low res. Most need to be rendered between 4,000 and 5,000 pixels wide at a minimum. To look crisp on render 20,000 x 10,000 pixels is good (a 2:1 ratio is the target for outdoor environments) A little math, if your visible spherical background is 10 percent of 360 degrees at 72 ppi then the total background width should be 36x10x72 or 25,920 pixels wide. Interpolation of the back ground at render helps keep resolutions managble. I do have some static backdrops that are 10,000 pixels wide for slow pans across a 16:9 field of view. 

As for indoor renderings, the proportions will require more experimenting if you will be doing an animated camera move. The reason is that the background room and the modeled area will need to be in agreement with perspective/lens adjustments. A Macro close-up won't seem to agree with a 50mm lens for the room. DOF can be your friend on this one.