I brewed the Cooper's as 6 gal, split into 3 LBKS. using booster instead of dextrose, and adding different Pride of Ringwood Hop treatments after looking at the Coopers AU recipes. It is a very fruity drink. The 2 different hop treatments were not much different in outcome.
Original recipe called for HME + 1.5kg LME + 500g DME + 300g Dextrose in 22.5L. Coopers adapts their volumes also in the recipes for different outcomes.
In 6 gal is it different from the Seasonal though.
So I translated to using DME only and Booster.
Cooper's Sparkling Ale #1
Cooper original recipe - 1/3 can HME + add 566g (20oz) light malt and 100g (4 oz) dextrose ( or 150g (5.3 oz) booster)
Cooper's Sparkling Ale #2 - original + 0.5 oz hop aroma 5 min boil Pride of Ringwood leave hops in.
Cooper's Sparkling Ale #3 -original + 0.5 oz hop 30 min steep tea Pride of Ringwood
https://www.aussiebrewmakers.com.au/libraries/resources/Pale Ale Recipes/Coopers Sparkling Ale.pdf
find these handy also, when looking at Cooper's brews:
With 3 LBKs, it works out reasonably, although I try to get the Cooper's HMEs on sale making it quite cheap.
However the recipe (23L) online is different from the refill kit that only contains 1.5kG of DME as additional fermentable.
So you can use what you want I guess. It still works out to < $50 for 3 LBKs if you only buy the Brew can from Coopers.