ok, so i like to tinker with stuff.... maybe that's why i am building small planes

anyway, i have this MVVS .91 that will go into my Cermark f-16

yes i could get a Jett... but where would the fun be in that? the f-16 is already an ARF so i have decided to put some work into the engine: porting

preliminary research shows the MVVS exhaust port should be raised 1.5 mm (no more, no less)

and i have found an article by Robert Thacker "Easy ducted-fan engine hop-ups" MAN March 2001

although the MVVS is not a DF, most of the mods are applicable (i think)... that's where i need some help

the questions:

1) in the article, Robert test-runs the engine & then makes some mods (porting etc) and then he test-runs again.... and so on
i thought the mods have to be made BEFORE the break in (?) obviously i was wrong, can someone explain pls?

2) the raising of the exhaust port is self-explanatory, but the mods on the intake side port he "contours so that it shoots the air to the front and top of the sleeve" am not sure what he means looking at the pic.... (?) can someone explain in more detail?

3) he lightens the piston by shaping-out a part of the piston skirt in a "arch" manner, he states:
"remember that the piston modification is on the front of the piston where the boost ports are, not in the rear of the engine where the exhaust ports are"
in my case, i have a side exhaust... would that affect the location of the lightning "arch" in the piston?

see pics

any advice would be great,
Vasek