What angle for sliding dovetail?

[smorgasbord]

I'm making a throat plate for my tablesaw, and it's going to have replaceable inserts that slide into the throat plate. I made a prototype and used the ubiquitous 14º dovetail bit, and I don't think that's enough since the insert is only about 4mm thick. Since then I've acquired 45º and 30º (from horizontal) dovetail bits. Both will flare out more than the 14º bit, but I'm wondering if the 45º will be too much and that the 30º will be better?

Any suggestions - at least for which to try first? The inserts themselves will be made on the tablesaw, so I can set the blade to either angle. My instinct says the 30º bit, but...