Re: Making your own bokken/tanto etc.
I really don't know much about woodworking.
The bokken I buy are 41 in (104 cm) overall, blade around 30 in (76 cm). I think the longer tsuka is a good call. Most bokken I've seen are between 9 and 11 in (23 - 28 cm), but I think around 14 in (35 cm) would be much better.
This is really a matter of personal taste, but you might want to consider making it with a non-pointed kissaki, in other words, a flat tip. I prefer it for training.
It'd be nice to see how it turns out. Maybe you can post some pictures when you are done. Also, I'd be curious to know how much it cost for materials and about how much time it took.
Good luck with your project.