If you can only install in the attic - do it.
This antenna is a 1/4wave 2m ground plane & the main vertical element and radials can be cut to work on 220 or 440.
Height is the most important item here - if it can be outside & higher or same height - set it up that way.
Use good vhf/uhf coax like 9913 - make 1 loop about 6-8 inched below feedpoint - use as little total length of coax, to get job done.
The radials are the 2nd part of the antenna - needs to work best.
Was in Las Vegas last month.....Do not remember most of it..............
73 K1WJ David