HPA VZ61 Skorpion

[Corkie121]

Bit of an information request:

Does anyone know what HPA engines will fit this little AEP?

I know that F1's and Jacks have been used, but has anyone had any luck using something mechanical like a PDIK?

I'm hoping that the lack of solenoid hanging out of the back makes it possible to fit the slightly longer mechanical systems but don't want to gamble +£200!