Made large bottom access hole 3.25" vs 3.125" to fit my large hand!
Largest hole saw I had was 2.5", so drilled it then used die grinder to open up to 3.25"
Top hole...elevator push rod Two 1" outside holes .... nut access for HS spar bolts Two 1 1/4" holes.... rudder cable through holes Bottom 3.25"..... access holes for nuts/bolts etc.