What's the gap in question? Master line specifically or just something in the whole lineup? If it's the latter I think the All-Road fits in there.
Idol Pro or All Road fits between those.
Master or Thunder really. I suppose the Idol Pro and Pearl might work but they both seem too close to the Phaze 3. Allroad, or really any road ball with that long lopey core tends to play under my IQ Tour.
There comes time where the Phaze 3 cover just doesn’t like the amount of friction, lack of head oil, etc and the IQ Tour is just not dynamic enough. That’s where I’m seeing taking a 2.48-2.52 RG/ .040-.053 diff symmetrical with a cover under R3S Hybrid.
That lead me to Axiom core 2.48/.050 with a mild cover, to think possibly a more dynamic IQ Tour to slot in there.
Just spitballing ideas really for a new release that would make sense I think.