When I've used Coopers Extracts I generally do something like the following.
Cooper's IPA 1.7Kg can of LME
Cooper's light malt 1.5Kg can of LME
Brown sugar 500Gr
Partial boil 2.5 Gallon for 60 mins with a little of the light LME, sugar, 1 Oz of Nugget or Magnum in from the start and then 1 Oz Cascade or Centennial at 10-15 mins 'til flame out. Then add my the bulk of my extracts. Cool down wort a bit, add to fermenter and top off to 21 litres. Pitch yeast when cool enough and let ferment in primary for three weeks.
Have had some pretty good results like that with high 6-7.something %ers
There's a member on here with the username unionrdr who's got some good recipes and notes for using the Cooper's HMEs