When installing the nosegear leg I decided to drill the 3/8" holes already for the engine mount. Chapter 46 can be downloaded from Van's revision pages. I started with bolting the nosegear leg to the firewall with an AN3 bolt. Thereafter I used a 1/4" reamer as the initial drill. Unibit 3/8" was next. With the unibit you're not able to complete the hole completely. Took off the noseger leg and completed the hole in the firewall with the unibit as far as possible and used a 3/8" (or 9,5mm) drill to complete the hole. I used an AN6 bolt and the engine mount standoff to bolt the nosegear leg back to the firewall and then repeated the steps for the left hole.
