Growing Solo 401K via Note to Trustee?

[Account Closed]

I have a self-directed 401K (solo 401k), and purchasing real estate for buy and hold. However, I would like to grow it by taking after tax dollars (W2) and issuing myself a promissory note of 50K but instead of doing “minimum” payments of prime + 1%, could I artificially increase it to say prime + 5%? Is there a max limit? Also checking with my custodian but wanted to solicit input on whether that would be ”prohibitive”. Thanks for the input.