Max dimensions would help in designing each octo to capitalize on space, but assuming a regular octagon with constant depth.
To get you in the ballpark it will be
Vol of each octagon =4*length of side*("diameter" of octagon)*depth
the diameter will be the distance form the midpoint of one side to the midpoint of the side directly opposite. This version for the volume should make it a tad easier to play around with the numbers to fit your dimensions
Assuming I did the basic maths right. Maybe someone else can check or I can check tomorrow after I catch up on sleep. Also keep in mind you still have to worry about thickness of the wood.
2016 Scion iM
- Bone stock for now