Playing with bike geometry

Over-forking bikes is a big thing at the moment. Many bikes are even designed around having extra travel up front. I went the opposite way with my Ibis.

My Slash has 150mm rear and 160mm front. This 1cm extra up front is frequently found. Yeti even seems to like adding 2cm up front!
Ibis designed the Ripley4 to take a 130mm fork with a 120mm rear end. However, they specified (tested, approved) a 10mm change either way without messing up either the handling or the frame security (nothing is going to fail dramatically). When I read that - a lot of people racing Ripley3s on techy races (think BCBR) had gone down to a 120mm fork, but had some pedal-strike issues; so Ibis raised the bottom bracket height by 7mm in the Ripley4 - I knew I'd found my bike.
I'm running a 120mm fork (even though most Aussie purchasers are going with the 140mm fork, making the bike ideal for almost all the trails in the country). The "rule of thumb" for changes is that it makes a 1/2 degree alteration for a 10mm change up front. I delved into the trigonometry to find out for myself.

I'll save you the sine and cosine work I got up to. The 130mm Fox 34 has an AC length of 537mm and runs 26mm of sag (reducing the AC to 511mm). My 120mm Fox 34SC has an AC length of 531.5mm and runs 24mm of sag (reducing the AC to 507.5mm). The difference is small! Only 5.5mm at full height and only 3.5mm at sag.
I ran the calculations using the full AC height.

Assuming that the physical angle between the frame and fork doesn't change (how could it?) and that the decrease happens entirely between the headtube and the ground I calculate a .22 degree increase in head angle and a 2.5mm decrease in wheelbase. The differences will be 30% less at sag. I wonder if anyone can actually feel such a minuscule change?

It certainly helps that the bike is long. A short wheelbase bike would see larger changes. Another part of this is that the 34SC is 4mm taller in AC than the 120mm 34 regular model.