Keith - Great looking chairs. Looks like you used the New Yankee Workshop plans. That's what I use and they yield a great looking and comfortable chair. I install the back slats so that they are centered and touching at the bottom and equally spaced at the top with the outside of the outer slats touching the arms. Gives the back a fanning out appearance that is very pleasing.
I made a set of 3/4 size templates for the chair. This makes a smaller chair that is very popular with grandparents. They paint, decorate, etc. and give to the grandchildren.
I have never used Deft exterior oil. What application process did you use - brush, spray, etc?
Again, good looking chairs. - John
You are right about the plan. After this picture was taken I added a horizontial piece near the top of the back to provide more support. Without the additional piece I felt the backs were just too flexible.
Deft is applied like most penetrating finishes. Flood the surface, let it soak in, reapply as needed, then wipe off the excess. It has held up OK but needs to be refurbished every couple of years.