Using tIRA money to pay the Roth conversion taxes vs taxable accounts is often said to be a no-no. Sure, you end up with lower balances it the accounts. I personallty don't think it is a loosing situation. At least in most cases. If one looks not to the dollar amount in the account, but to what that dollar amount buys you on the withdrawal end, it is mostly a wash. It could even be a benefit if in a lower tax bracket at the time of conversion. Looking at RMD time, we will definitely be in a higher tax bracket. And when either I or my wife leave this world and the survivor is filing as single, it changes the picture even more so in favor of paying taxes now at the lower or equal tax rate.
Sorry, I have not examples to show. There are too many assumptions and variables to go thru to prove my point.