Au contraire, fltlt, size does matter. Stealth measures reduce RCS, so if you have a B747 sized target and apply Stealth techniques you might end up with a Tornado sized RCS (ie. Still pretty frickin' huge), but if you take a Tornado sized target and apply Stealth techniques you might end up with a golf-ball sized RCS(ie. Pretty frickin' small) - so size is applicable with stealth.
Looking at RQ-170 I see a compromise over minor stealth tweaks, economical concerns (full stealth is frickin' expensive and labour intensive) and aerodynamic performance (that looks like a high lift wing with very little stealth). I agree with others on here that RQ-170 is not a full stealth platform design like B2, F117 or F22.
LJ