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Don't you mean 15cm in real size? Cause if it's only 15mm that would be 0.2mm in 1/72nd scale and not worth the bother.
The engine cowling is too long of about 1.5mm for A-6 variant. So for A-4 it is too long of 3.5mm in total. Please check my thread about the Academy model you will find there some info on that. You might find that interesting.
http://www.ww2aircraft.net/forum/group-builds/fw190a6-sturmjager-sturmstaffel1-16915.html
Thanks for the link Wojtek. Yes, I remember that particular project of yours. Some impressive work and serious "model surgery" going on there. Once I start working on this model I intend to address some of the issues you pointed out to achieve better accuracy, but not to the same extent due to my lack of your level of skill and limited time frame of the group build itself. We'll see how it goes...