Pertronix question about timing

I fitted a Pertronix Ignitor contactless ignition system to my 1977 Carrera 3.0, replacing the originally fitted ignition points. Specs on rear decklid state setting timing to 5degrees after tdc at tickover, and this is borne out by other specs for my engine. This worked ok with the original points but with the Pertronix contactless system the engine is severely down on power especially on hills. All indications were that timing was severely retarded. I advanced the ignition timing to TDC and then to 5degrees BEFORE tdc and power seemed to be restored. I haven't risked advancing further, really concerned about holing a piston. Why do I need to alter the timing though? What are the differences in characteristics that create this need for such a huge change in timing? And, should I just set so that absolute max advance is 36-38 degrees at max engine speed and ignore the tickover advance?

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[Casey at Pelican Parts]

I am hesitant to offer advice on this, were there no instructions that came with the kit? I would verify that the vacuum hoses (if equipped) are properly routed.

- Casey