Milling replacement for 70 y.o. redwood shiplap siding.

[tomtheelder2020]

Some of the 1" V Shiplap redwood siding on my house is in pretty bad shape but this pattern is not available from any supplier (similar but different dimensions is available). I plan to use my table saw to mill new pieces from marine plywood because redwood is more than double the cost per foot. I plan to prime and paint all surfaces. Does anyone have suggestions for other steps I can take to increase the longivity of these pieces?

 

[DFBonnett]

When priming use a slow drying (long oil) exterior rated oil based primer. Pay special attention to the butt ends on any piece.

 

[tomtheelder2020]

Good idea. I did not think about end grain before - and with plywood all 4 edges have end grain. The top edge will be well protected but for the other sides I have some PC Woody hardener that will soak in deeply.