You'd have to use actual numbers to know for sure, but I think you're going to end up paying more in taxes this way. The 12% bracket is up to $38,700 for single filers. Add in the $12k standard deduction, and you can have $50,700 in income and have a 12% top marginal rate.

If your projected income in retirement is less than $50,700, then you'd likely be better off waiting to pay. You could lock in a 12% rate now, or if your conversion amount in retirement is $30k, for example, then you would end up paying 0% on the first $12k, 10% on the next $9525, and 12% on the remaining $8475. That's a total tax of $1969.50, or 6.57%.