Is there a provision for changing the size of the siphon break in the metering blocks (some have them, others are simply drilled into the angle channel)? Enlarging them "should" delay the point at which the main circuit comes into play, but that's just the first thing that came to mind. Any room to lower the float level w/o causing a lean hesitation? That would have an effect on how quickly the mains comes in, too.

Not sure if there's something in the emulsion stack that can be tweaked to make a similar change w/o messing up the AFR curve.

Also, I've worked w/ Dom on carb stuff in the past, so we're not strangers.

EDIT: I looked a few pics of the Titan-style metering blocks and none of the blocks shown had siphon breaks in the angle channels. Unless there's something radically different about how they function vs a "traditional" Holley-style metering block, I think not having siphon breaks is very likely a contributor to the main circuits coming in too quickly.