G'day Rockhoppin
Have you had a chance to play with the blank?
I have the BWS275-4. I haven't finished making it yet so haven't fished it, but. I had the chance play with the whole range in my local store. I purchased the blank for the same reason and casting weights as you. The BWS275-6 felt an over kill for what I wanted (Spinning with 14lb braid,20- 50g ) so I went for the BWS275-4. The BWS275-4 feels as though it call easily fish 6kg. I know a fellow who said he fishes 20lb on his.
But if your not sure and can't get to play with them before ordering, the BWS275-6 would be a safe bet.
Cheers
Anthony