Dose va extraction time : Coffee

I’m using the blend below on a Rancilio Silvia V6 and Rocky Grinder.

(Complete beginner)

The recipe states:

• dose: 21g

• time: 27-32s

• ratio: 1:1.8

On my 18g basket, I can comfortably fit 16g, but no more.

Therefore: 16g (dose) x 1.8 (ratio) = 28.8g = 28.8ml of espresso

So I still need to achieve an extraction time of 27s-32s for my new dose – correct?

If I purchase a triple basket (which can fit the recommended 21g dose), then I still need to extract in that range.

Between changing dose, something probably needs to change to stay in that extraction time window (if I keep my same grind setting and just up the dose, my extraction will all of a sudden be too slow, won’t it?)

Am I correct in assuming that I would need to adjust to a slightly courser grind setting for a larger dose?

My beans: https://www.padrecoffee.com.au/collections/espresso-coffees/products/daddys-girl-espresso-blend

Thanks for your help!