Installed motor mount. Located on fuselage and marked area on the lower mount brackets to trim for the taildragger main gear tubes. Trimmed the lower mounts and clamped the mount into place to one side to get an estimate of the shims needed, made shims. Put them in place to center the mount and found they weren't thick enough (tried .060 per side on the top, .090 per side on the bottom). Both were not thick enough. Moved the .090's to the top, and tried to get the caliper in the bottom to measure, but instead pushed some .125 scraps into each side. Made up .125 shims for each side and found they were too thick. Made some .025 shims for each side to add to the .090's. Ended up using the .025 only on one side. It's not easy to decide that the mount is level side to side, as the top cross beam wasn't square with the mounting lugs (side to side). I decided that the gear is more likely level with the cross beam, and if the motor itself is tilted a little, then that's ok so long as it's still level front to back and left to right (this whole discrepancy is well under 1 degree). So I leveled the upper cross beam and set it equidistant from the firewall forward cross beam to set left and right, then checked level front to back using the dimension up from the bottom plane of the fuselage to the lower mount boss. Drilled out to 3/16 anticipating using a 3/16 countersink cutter then drilling up to final size, but turned out to have a 1/4 c-sink cutter. Made a practice part to set the depth on the cutter - set to leave .020 of material above a knife edge in the .125 (as others have done). This leaves the bolt heads a little high on the surface. Did 2 holes like this and quit for the day.
