Size of splines?

[J.R. Rutter]

If it were me, I would proceed as you first mentioned and assemble the joints. Then just make a series of 1/8" kerf slots spaced, say, 1/4" apart and glue splines in. This gives you massive glue surface area and good depth using the blade that you have.

[John TenEyck]

You seem to be hung up on using splines when loose tenons (or dowels) would be so much easier and stronger. That's your business, of course; just seems like a lot of effort for no advantage and lots of potential problems.

John