Acid Cherry tree Pruning

Zoe2

Hello,

I bought what was supposed to be a 3-4 yr old fan Morello cherry tree 2 yrs ago.After 2 yrs of trying to prune this tree,I now think it is infact a spindle pruned tree(it still has it's original leader and about four laterals coming off this each side).I would like to cut the leader down to above the first two laterals and try to make it into a proper fan,but could anyone tell me if the tree is now too old to do this please?  Thankyou.