I would agree if we were talking about a bike already designed to be nervous, but you should be able to read a book while riding that Arenberg.
Since I'm on vacation and my coffee is too hot to drink I decided to mock it up in bike cad using the geometry chart from above with the fork length(368) and headset stack height(12mm) listed in it(1'st picture). Then I changed only
the fork offset from 40mm to 43mm(second pic). In the third I kept the additional 3 mm offset, and added 4mm to the fork length 1.7 mm to the bottom stack height.
stock 55 Arenberg.JPG [ 95.75 KiB | Viewed 922 times ]
Stock 55 Arenberg + 3 mm fork offset.JPG [ 95.28 KiB | Viewed 922 times ]
Stock 55 Arenberg + 3mm offset + 4mm fork length + 1.7mm bottom headset cup.JPG [ 93.3 KiB | Viewed 922 times ]
Judge for yourself, but imo when starting out with the stock 55 geometry it would be really difficult to render that
bike unstable with such a small change in fork offset.
To the OP do you have or have you had another bike that you could ride no hands( same saddle height/setback and cleat placement)?