Retail capital will stack on a second position under 2 conditions:

-As long as that first position lender is not a NAMAA member, http://northamericanmaa.org/category/our-members/
-There is enough gross they can squeak out. Retail rarely stacks on top of On Deck because they are known for eating into a lot of the gross on a first position

However, you may want to heed Sean Bash advice.....