Ummmmm..... what do you mean "do not use the screw supplied"?
Or....are you talking about some screw supplied with the NP RS-X base?
AFAIK no screw or base is supplied with the Phantom.
The entire mast track system is a "knock off" of the others I mentioned, made to a Cobra specification, and the pin is slightly different.
I had to ask Starboard HQ to get me the correct pin/universal assembly from the same supplier that made the mast track for the Phantom 301 I had last year.
Once I got the correct part, you simply insert the base and lock it down with the little black plastic actuator tab at the front of the mast track car.
Check this URL to see if you have the same board I'm familiar with:
If you have something different, then I may be incorrect, but both the Phantom and the Phantom Race proto I had last year had the same adjustable mast track, made to the Cobra specification and it required the "special" pin.
The pin for the Exocet race boards (with a sliding mast track) were the closest, but the correct part fit very nicely and was very secure.
It may indeed be the same pin set up as the RS-X Olympic board, but I did not try an RS-X base in either of the Phantoms I had.
As to "how the ?? do you put in the mast base, that's easily answered.
Get the correct pin/universal setup and then it fits just like any other board with a pin type (on the bottom, not a Euro Pin top) sliding mast track setup.
The pin bases I was supplied with came with the "special" Cobra pin on the bottom and a std. Euro pin on the top, with a WSH/Chinook/US adapter over the Euro pin on the top.
Only problem I had was the locking slider for the adapter tended to get stuck with the downhaul line if you were not careful to put the line up the back and the lock plate tab on the front.
Hope this helps,