This is tricky.  The rules are sketchy and IRS “could” claim since you took custody that its no longer sheltered.  I had this EXACT conversation with a senior manager at Bernstein. 
Swan offers a custody solution for a fee 
Unchained offers a self custody option that id be more comfortable with now that the political landscape has shifted towards btc friendly policy.
None of this has been tested yet.
👊🏻🍻🧡