Cutting the thruster holes

Thruster holes, stern After trying for a long time to calculate the size of the thruster holes by mathematical means I resorted to cutting out circular holes, and spending a few hours grinding them into the desired shape and size by trying again and again.

Bow thruster, test fitting Really, with the bow and stern slanting in two angles I found it next to impossible to get a grip on the formulas. Event then, how do you paint a decent ellipse on a slanted piece of wood? Anyway, the crude approach worked, and the gaps I inadvertedly created hopefully can be bridged by epoxy glue.