A little info on moisture meters....They are only as good as the person using them.
Also money saved is money lost.
If you think for a minute at all the different types of wood that you may want to use in building a bow and how different that each of these are in density that a single non adjustable moisture meter will be able to give you an accurate reading on them. Oh, it may work on some but which ones?
There is adjustable density numbers for each species (Most all species) and if your reader has flexibility to be set to these different numbers, you are somewhat further along.
I have a mini ligno DX and it has 20 different settings. They have meters out there that are even more sofisitcated but even with a good reading, you will only know the actual mc at the depth of the probes or about 1/4" for the pinless meters.
The core will almost always be a percent or more wetter than the outside.
The rate at which wood dries is completely dependent on its enviroment. Is it stored outside with no airflow but under a shed? does it have ample airflow...big difference.
stored in closed building but no airflow?
stored in climate controlled building? add more airflow and it will dry even quicker.
Dry too quick and it may check or crack badly.
There are many ways of expediting wood drying, but it can be expensive if you don't know what you are doing.
If you have an adjustable moisture meter and it is set on the number for Koa. Probe it in an inconspicuous place...there's so much waste in a riser block and I've never had an issue with probe marks.
If the moisture is good on the outside...not barely but in the range, I would make the deepest cut that you can in that block. Surely you aren't going to leave it completely whole?
Now probe it again and if it is good on mc, build a bow. If not, put it back in a climate controlled place or microwave it to get it ready to use...better read up on the microwave thing first before you burn down your house
BigJIm