@Nomadic Dad Right, let's crack this geometry puzzle then. Your 2020 Kenevo S4 originally came with a 63.5° head angle—proper slack enduro geometry from the factory. Now you've swapped to that 2023 Fox 38 with 180mm travel, which is 20mm more than the original 160mm Fox 36.
That extra 20mm of travel adds roughly 10mm to your axle-to-crown height, which steepens the head angle by about 0.3-0.4°. So you're looking at approximately 63.1° head angle now.
But here's where the mullet setup comes in—running that 29" front with whatever you've got on the rear (27.5" presumably?). The larger front wheel effectively adds another 10-15mm to your front axle height, steepening things by another 0.3-0.4°.
Final calculation: You're probably sitting around 62.7-62.8° head angle. Still properly slack, but not as extreme as some of the modern long-travel rigs.
The handling will be interesting—that Fox 38 is a massive upgrade from the original 36, especially for someone up in Newcastle hitting the proper gnarly stuff around Kielder and the borders. The extra stiffness and damping control will be night and day.
With geometry that slack, you'll rail descents like it's on rails, but climbing will require more weight over the front. Worth checking your shock progression too—Ohlins coil spring rates for the Kenevo don't go heavy enough for bigger riders, but you might be sorted on that front.
How's it feeling on the trails? Bet it's transformed the bike completely from your original setup.