I didn't mean to disparage the quality of the Lava Dome/Cinder Cone frames - as you say, they were made of double-butted 4130 and had better tubesets than the Fire Mountain, but the Kilauea and Explosif were made of high-end tubesets, which were stronger, weight for weight. So they were mid-level in Kona terms, but to put that in context, Kona put emphasis on frames more than kit, which is why the Lava Dome was widely considered to be the classic upgradeable mid-range bike of the 90s - it had a better quality frame but worse kit than other mass-produced bikes at the same price level. The banter on this site appears to be between those who think two frames made of the same tubeset are much the same and those who think that if one of them was made in the USA and therefore cost more, it was better. So for example, Fat Chance Buckshavers and Rocky Mountain Hammers had similar-quality tubesets to Domes/Cones, but were built in North America. Each to his own, I say, but I think it's this 'upgradeable' quality which is the key to there being so many Domes/Cones still in active use and featured on this site.
There were in fact four different kinds of Tange Ultimate - from Superlight to Ultrastrong (all with 0.6-gauge seat tubes though). Clearly you can use the strengthening properties of heat-treating to do one of two things - either achieve the same strength with a lighter tube, or achieve a greater strength with a standard weight tube. If you have a frame entirely made of Ultrastrong, I would guess it would be in the latter category, and it wouldn't necessarily be all that light.
But having said that, 4.48 isn't bad for a size 19. Although there were variations between years, I think my Kona frames give an illustration of the range of weights involved (all normalised to size 18 ) - Tange Prestige Concept 4.4, Columbus Max 4.2, Columbus Cyber 4.3, Reynolds 853 4.5, generic 4130 4.8. All just about the same strength, but using different amounts of metal to achieve it. The Columbus Max frame probably the stiffest, and the 853 built for strength not light weight (my Merlin Rock Lobster 853 with skinnier tubes weighs 4.25). So the weights of your Konas surprise me. 4.31 for a size 14 isn't so surprising, as judging from my size 16 97 Lava Dome (4.55), I would have thought a 14 would weigh 4.4. But all the tests I've seen for size 18 Cones/Domes say 4.8, and Kona themselves claimed 4.75, so I find that 4.41 quite surprising. But anyway, irrespective of all that, I still think it has a 9-7-13 seat tube and I personally would leave it that way. Even though it's only a Kona. After all, if it snapped, it could be a Kona stuck in your leg.