You can map hotcues 5 – 8 by adding a modifier which acts like a shift key, then use 1:5, 2:6, etc. If you’re not sure how to do it, open your S2 mapping and look at how hotcues 1-4 are mapped, then just apply the same/similar settings for the additional hotcues.
Or select add in, track deck –> cue –> map hotcue, then select hotcue type 1-8, deck target, and choose your modifier. Probably a button you don’t use much. You can decide to make it a toggle switch or hold switch.
I would also, for simplicity, recommend getting an X1. This will grant you 1-8, along with giving you additional control over FX and transport for deck C and D should you choose. I’ve seen used models for <$100.
Good luck.