Up zoning on a 4 units multi family to a 6 units in Pilsen

[Leonce Barrigah]

I recently purchased a 4 units residential on 18th street. It's essentially a two stories plus a basement. Each floor (1st and 2nd) has two units. And the basement (two separate entrances) is identical to the units above it from a size perspective. The basement height conforms to that of what would qualify as a legal unit (7.5). I'm very tempted to turn the basement with separate entrances to two legal 1bed/1bath units. The issue is that the property is currently zoned as a C1-2 but grandfathered a RT-4 which means that for me to be able to do that, I'd need to get it rezoned to RM-6. Anyone ever done something similar and willing to share insights? Or is it just impossible to do? Another alternative would be to duplex down to the basement but the additional two units have a bigger potential for return in my opinion.