Solo 401k - using both Traditional and Roth for investment

[David Gwilt]

I am going to be doing a debt consolidation loan to my brother-in-law using my Traditional and Roth Solo 401k (because I don't have enough in any single account).  I have opened the Solo 401k checkbook accounts and have a separate account for each the Traditional and Solo 401k.  For payment of the loan amounts, do I need to have him make out two separate checks/transfers each month or can one check be deposited into the Traditional account and then immediately transfer the appropriate amount to the Roth account (based on % of initial loan amount)?  This is my first time doing this and I could use some guidance.