Hi Brett,
Have you had a look at our new flat top grind blades that are made for fine cross-cuts? We offer them in two kerfs, 1/4" and 5/32". Soon we will have spacers that you can put in between the two blades to make 3/8" wide grooves with flat bottoms.
Please see the link below.
http://www.infinitytools.com/products.asp?dept=1484
Thank you,
David Venditto
Infinity Cutting Tools