Hemisphere pans - what am I doing wrong?!

[Superherosidekick]

Bought the 6 inch lakeland hemisphere pan. 2 attempts now and the cake sinks in the middle leaving it with a hollow. Standard sponge recipe and I have reduced oven temperature as suggested. Any ideas what is going wrong? Would I be better off with a Madeira recipe?

Yes a Madeira would probably hold better.

The pans are a bit of a faff. I had to experiment with a couple of batches before I got it right.

Do you use an all in one sponge or a cream the butter and sugar recipe?

Not all in one method. DS wanted a piñata cake so he might get one LOL!