Principally rhymes with:
accompli, amply, bapley, capley, cheaply, chipley, copley, coupley, crisply, cropley, deeply, epley, eppley, harpley, kepley, lampley, leapley, lepley, panoply, rampley, rapley, reapply, ripley, rupley, sampley, shapely, shapley, sharpley, sharply, shepley, shipley, simply, stampley, stapley, steeply, supplee, tapley, tarpley, teply, whelpley
Principally sounds like:
permissible, princeville, principal, principle