H. Edward Hales, Jr. (Sutherland, Asbill & Brennen — Atlanta) has published Thinking About Leveraging Plan Assets?  Think Some More:  UBTI and Prohibited Transactions, 39 Real Prop., Prob. & Tr. J. 541 (2004).  Here is the abstract:

This Article discusses the use of leverage in the context of qualified plans. More specifically, the author addresses whether leveraged investments will expose a qualified plan to tax liability on unrelated business taxable income and whether the investments will violate provisions of the Internal Revenue Code and ERISA. Exclusions for acquisition indebtedness are discussed, as well as exemptions under the ERISA and Internal Revenue Code prohibited transaction rules. The author concludes that although the use of leverage can be risky for qualified plans, it can also be a great tool, given proper planning and a thorough understanding of the relevant exclusions and exemptions.