So I finally killed Ucamulbas. Quest time was about 42 minutes, I guess. I was using the same Camellia/Butterfly setup as the last time. 
That was a pretty hairy fight - I ran out of every healing item, lost 2 lives, and my last Hot Drink cut out just before the quest ended.  But I killed it all the same.
The funniest thing is that after killing it I went to the armoursmith to use the new upgrades... and discovered that, other than my headgear, none of my armour had been upgraded at all.  Σ(ﾟдﾟ;)  Oops.
 
Edit: Here's my gear setup.
Weapon - Wyvern Blade Camellia
Armour - Full Butterfly X gear, 434 defense due to dumbass mistake
Jewels - 2 Artisan, 2 Expert,  2 Master,  1 Celebrity, 1 Hermit
Skills - Evade +2, Gathering +1, Reckless Abandon +1, Sharpness +1, Cold Increase [Lo]
 
Edit 2: Before you ask, no, I haven't done the Monster Hunter quest, and no, I haven't tackled G-rank Fatalis yet. All things in good time - anyway those are "extra" right? ;)