Laid-out initially. Taped-down the GPS antenna cable to provide a straight line. Determined where the GPS antenna would be and cut a slit in the material for it to protrude. The antenna cable surfaces thru the glareshield at the aft of the tank, which is about 1.5" in front of the compass mount shown in pic 3. Since the GPS antenna has a strong permanent magnet (bad for compass!), standard practice is to mount it as far away as practical, hence it extending to the front of the glareshield.
Inserted the rubber grommets for the compass mount and used a small drill to locate the hole locations. Trimmed away material using a razor.
Glued down the top surface only of the material. Inserted screws to attach compass mount.