Thanks Carp13. Me hit with rock and it no work.
The key to this type of mod is to be sure the mag face touches the bottom of the gun body and the ball pusher (in the magazine) enters the body enough to put the ball in the chamber. You will have to remove enough material from both the gun body and the magwell that you have chosen to adapt.
For 98's I cut to the depth of the forward air channel. Pics above are cut to the width of a Tippmann magwell. Because 98's are clam shells, locating the center for the bottom hole is easy. Center it under the top feed hole of right half. Also try not to eliminate the bottom front screw location. you need to have the halves tight to keep the barrel in place.
Finally, this design does not have a detent. It relies on the ball being under pressure from below. When you close the old feed port, you may want to add a detent there.