yes, tank is small, bike is light & so on (but supernimble). sure it is not really ideally suited for high speed Interstates but really how many bikes/riders are? my 125 mph 640 lb Sports Cruiser has the world's most advanced suspension (it's a BMW) but if I hit a nice bump on the Interstate (as we did today!) I/we/the bike still feel it.
I have wound my (basically) modified Savage up to 85 without much trouble (which judging by those "Your Speed Is..." signs on the highway is pretty accurate, unlike many "speedos" that are optimistic) with a fork brace on & in pretty calm weather & found it a little squirrely.
I concur with my friend thumperclone who over a beer said he is happiest @ around 65 cruising - keeps you out of way of most vehicles - you get used to allowing for the blast of wind when big semis go past.
if you wanted a steadier bike for higher Interstate speeds I also concur with others - maybe consider a heavier bike. however, Kathe for one loves the Savage for its lightness (she is a tad more than 104 lbs - shhh! - & 5' 9" but likes the seat height too). when I bought it she wanted to learn to ride for the first time in her life - via an MSF course, naturally.
I, as I said, love its nimbleness, which you'd lose on any other "comparable" bike, as it takes me back to simpler, "lighter" (me & bikes!) days. (I know nimbleness is likely not a "real" word, but there you go - sorry).