CRX
(CRX)
7
What light are you building, I’m guessing this pill is from a light that has a reflector?
Your new triple MCPCB & optic will only be around 7mm high, the reflector will most likely be taller than this so you need to make up the extra space, usually with a copper or aluminium spacer.
Plus it’s good to have a chunk of metal as a heat sink for triple builds.

Example:

Ideally you would want both sides of that drivers negative ring to be securely tightened to the pill or soldered for dissipating heat and the thermal control.
You could make a brass or copper extension piece to fit under the retaining ring if you’re going to deepen the driver cavity a little. Tightening down on the chips risks breaking them.