[SteveinTO]

"Any suggestions as to whether I might be able to lower the rear 0.5 inches by these adjusters?"

Depends on where the last guy left them. And no way will the adjusters be adjusted symmetrical side to side.

In a perfect world you'd center the adjuster, then index the spring plate with Wil Ferch's calculator based on torsion bar strength, car weight, & your hat size and ride height would be almost right on. Then you'd fine tune adjust with the bolt/eccentric adjusters.

Me, I've only proven the definition of insanity, that is "trying the same thing over and over again expecting a different result."