I decided to try your technique - I just added 16 capsules of ReefHD Reef Flux (fluconazole) at a 4x dose (16 capsules for a 43 gallon system including the sump; I'm assuming that at least 3 gallons are taken up by live rock volume etc).
My tank has a variety of soft corals/LPS as well as a coco worm and various macroalgae (none Caulerpa, but including Dragon's Breath, Chaetomorpha, red Gracilaria, some recent blue Hypnea, and a red bubble grape macro). 1 fish, 1 shrimp + 1 pistol shrimp that I never see, and a few hermits with a bunch of snails.
Today is Day 0; I was mildly surprised that the fluconazole doesn't dissolve easily, and that opening each capsule is kind of a pain!
I'm hoping for Valonia eradication over 4 weeks without harm to other inhabitants.
I went with this over Vibrant as I've read mixed things about Vibrant vs Valonia, as well as chaeto not doing well with Vibrant and this seeming like a reasonably safe, effective "kill the pest algae" treatment after reading how it's the premier treatment for Bryopsis.