Which brokers will accept my gold-ETF shares as collateral in a futures account? Schwab's cash only.

I added it up. It will take 105 GLD contracts to tail-hedge my gold ETF. Ugh. Plus, the hedge gets rolled each month, so 105 x 2 x 12 = 2520 transacted contracts. Double ugh. I've heard about options on futures contracts, and by using /MGC I can get the tail-hedge down to 12 contracts. That seemed a promising route until I learned Schwab only accepts cash as collateral, but admits that other brokers accept non-cash collateral. So can anyone recommend a well-established broker who can accomodate? Also, I'm a newbie to futures and options on futures, so I'd appreciate wisdom from people who are comfortable in this world.