Slow Motion by Duration

Can you add the ability to set a Slo Mo speed by duration? Like I have a realtime clip that is 22 seconds and I’d like to slow it to 1 minte 30 seconds. That’s not easily solved wit 2x, 3x, 4x as your choices. So maybe a Duration slider or Output Duration field.
That said, this product is AMAZING! thanks for all you do!