How much timing is too much for cold idle with no IAC?

I've got a DC2.2 cammed k20 with Haltech Elite 1500 driving it, and don't have an IAC fitted. The cold idle was pretty bad out of the gate, but I spent a bit of time tinkering with it and found what seems to be the sweet spot based on the 0-25 degree timing guideline mentioned in the cold start tuning webinar..or maybe it was the idle tuning webinar, I'm not sure at this point. I've got my throttle screw set to a point that idles at 1000rpm with no idle control and base IGT at 10 degrees BTDC, and when idle control is on it pulls about 6 degrees from the base timing degrees BTDC to hit my 950rpm idle target.

When it's cold, 70 degrees for example, I've got ignition timing correction set to allow it to advance up to 15 degrees until the coolant reaches 100 degrees, at which point it has less trouble idling and the limit is increased to 12. With it using the full 15 degrees I give it, I see it float around 850-875 with the timing up around 25 degrees BTDC. 850-875 isn't super great, but it's pretty close. I'm pretty sure colder temps will be worse, though. The engine doesn't show signs of knock at these revs, at least when cold, but I'm curious...how can I tell if I can safely give it more? I don't know how I might determine what MBT is at these RPMs, let alone know if I'm anywhere near it, but I don't want to melt pistons or torch the exhaust. Would I use an exhaust pyrometer to verify safety? I tried bumping the screw in a bit further and pulling more timing when hot, but the hot idle quality starts to suffer noticeably much below 6 degrees BTDC.

--Matt