Will Klipsch Forte IV's Work In A Smaller Room?

You could make it work at midfield distances.

If you are set up on the long wall of 12.5 ft,

Pull them 1 ft from front wall and leave around 4.5 feet behind seat and back wall. Such a listening position would position the listener out of some some problematic lengthwise modes in the room. It would imply a 7 feet midfield listening distance from the speakers, which is enough distance for the drivers to sum properly. Corner loading is a hindrance to perceivable resolution. Hence, don't put the Klipsches on the corners and set them up 6 feet apart, resulting in a 6-7-7 isosceles triangle.

Place a sub each on each sidewall behind your seat to address widthwise nulls. The subs can be good performance micro subs like the kef kc62 for the small room.

Play with toe-in until you get a good amount of envelopment working with the space behind you. 

I bought my kid a pair of bookshelves, 2 ways with a 6.5” woofer and in his 9x11’ room bass was overwhelming. Was it flat?, neutral? Nope, was it fun h e l l yes.

Yes

A couple of years ago I made a wood structure that tied my Cornwalls together precisely as to toe-in and distance between the speakers as well as distance to the rear wall. Everything was linked together on a common track so that all variables could be duplicated precisely and in unison by measuring against the back wall with a spring coiled tape measure.

Each speaker was linked to the track at at a hinged back corner which became a pivot point for toe-in. It was then that I gained an appreciation for precise speaker placement without wrangling with tape markers and all the rest of it. If you can adjust speakers accurately without having to fuss with it, then you are more likely to play with variables to your heart’s content and get a feel for what is going on in your room.

My listening room has pine floors to which the apparatus could be attached.

You don’t need high efficiency speakers in that room unless you’re trying to peel the wallpaper.  I have 87db speakers with 6watts of set power in an 11x14 room.  Average listening volumes of 65-70db with peaks in the low 80’s.  Very satisfying for my tastes.