I'm not good at this....! Hence the call for advice. I'm minded to follow the method where you weigh the eggs first then use the same weight of sugar, butter and SR flour, but how many eggs should I use? Also, I use Homepride SR flour which says it's pre-sieved, but would you sieve it again anyway? I really need this sponge to rise well.. 
(Btw the tin is 5cm deep)