Can a full sized 1911 be concealed effectively...
Yes...I did so for the first 7 years of my 17 years of EDC.
Barrel length, particularly when carrying IWB, has very little to do with a guns concealability.
Much bigger factors are the guns width and height as measured from the bottom of the mag well to the top of the slide.
1911's are still some of the thinnest auto pistols you can buy and come with what most agree is the best fighting trigger ever devised...short, crisp, and CONSISTANT!
Many years and many guns later I've come to the conclusion that the ideal "uber concealable" EDC gun "for me" is: A. No wider than 1" and B. No taller than 4"
For these reasons I've opted for a Kahr PM 9 simply because I work in office attire and must be able to hide my EDC under a tucked in button down shirt.
However, when winter attire allows, I still enjoy breaking out either my 5" Colt or my 4" Kimber, IWB with a dual mag pouch on the weak side...just to balance the weight.
Good Luck and be Safe!