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Perhaps he's asking before he invests in the hose.
Here's a thread you may find helpful.
http://www.scubaboard.com/forums/regulators/318570-fitting-miflex-hose-hollis-dc2-1st-stage.html
Here is an option to consider. Install your Hollis hose in your first stage. Install an adapter 9/16 male to 3/8 female on that hose's end, http://www.divegearexpress.com/regulators/adapters.shtml#34 add a miflex that makes up the rest of the length you want to the adapter and install your second stage.
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