: I did a search on staplers and staples, seems to be revisited often
: and a wide range of what to use. I have access to an electric
: Arrow stapler for free so hoping that will work in 4mm x 7/8ths
: Atlantic White Cedar

: -Pneumatic, electric, or manual

: -1/2" crown or 1/8th

: -preferred length - 5/8ths sounds like a winner

You should be OK with the electric Arrow (free is good), and if you change to an air stapler later, the stock of T50-type staples will fit the new gun.
Manual works well, if you are looking for hand exercise.
T50 (wide) staples are what I use; I've got a narrow crown stapler and definitely wouldn't use it on a strip project. Narrow crown staples make bigger holes and are a lot harder to remove.
Get a few different staple lengths and do some experimenting. The material you use for your forms can/will affect the penetration. NB- you can vary the driving force of the electric gun by more/less downward pressure .