Ali,

The JR servo is the 9411 in UK/US (9401 here in Asia/ Pacific). It is a 5Kg mini servo with metal gears and really is a mini 9411 I have used a lot of them in my jets such as the BobCats, Sabre and even in my Savex L39. with total success. It is a tight fit in the Hawk wing but it will go in. Metal gears remove the possibility of any bumping of the surface damaging the gear train.

I too would caution builders about the slotted flap mod. As I wrote earlier the pitch down problem was discovered on the original Hawk and was fixed by DELETING part of the slot on the outboard section of the flap. It might look more scale but COULD give you problems. Just a suggestion.
Regards, , David Gladwin.