J,
If you want to put those gauge of strings on then so be it, but my contention is that you don't need to. For B-B tuning on my 28.9" scale baritone I recommend string gauges of 0.014", 0.018" (or 0.023"w), 0.030", 0.039", 0.047", 0.065" (0r 0.070"). These are D'Addario EJ15's with the first string removed and an 0.070" added. This gives great tone and volume on the guitars I build. The string tension is pretty close to inbetween a set of EJ16's and EJ17's on a 25.5" scale length guitar in standard tuning.
Even if you go for the heavier sets and 230lbs plus tension I would not beef up the bracing - same arguments as for making a 12 string. I recently made a 10 string guitar-cittern with 230lb string tension and the bracing height and profile etc were as per normal. Sounds wonderful. I would pay a lot of attention, however, to keeping the bridge on under such tension and also long term neck stability.
I suspect I am in the minority of baritone builders with my views here, but hey variety is the spice of life. The proof of the pudding is in what I hear from the guitars I have made. I have a recording of my euro spruce/braz rw bari on my website
here. Go to Treebeard on the page.
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Dave White
De Faoite Stringed Instruments". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010