Questions Unable to Add Field "Unapplied Balance" to Generic Inquiry "Payments and Applications"

Our Billing department hit me with a GI request last night and I've been pulling my hair out over this for the past 12 hours 😥. Yesterday evening I was asked to pull the "unapplied balance" field into our Payments and Applications GI, and after a couple failed attempts + some forum surfing I found that this field "APPayment.CuryUnappliedBal" is simply not going to give me this information (because this is a calculation field).   

I then stumbled across the post below, where this individual seems to be encountering the exact same issue. Naturally I was very excited to see the "best answer" providing a different route to accomplish what I'm after... but I have since attempted to use the fix provided in this thread, to no avail. Much like the "APPayment.CuryUnappliedBal" field, "APRegisterReport.DocBal" is also pulling a blank column into my GI.  

https://community.acumatica.com/reports-and-generic-inquires-115/add-field-unapplied-balance-on-ap302000-to-generic-ap3020pl-12349?postid=47232#post47232

"Instead of using APPayment.CuryUnappliedBal, join APRegisterReport with APPayement and using field APPayment.CuryDocBal, schema field is APRegisterReport.DocBal It will show the amount of unapplied"

I'm at a loss and I'm very much hoping that someone in the AUG community has an answer to this problem. 

Thank You,