I got a similar gap with the Ritchey Switch headset I´m using. I glued a thicker 1.5mm rubber seal to the headset cap to close that gap.

What seal did you use and where did you get it? That seems like a great idea.

Anyone dealing with a larger gap than usual between the head tube and first spacer despite being aligned and tightened down? Looks to be about 1mm or slightly more versus the usual .5mm of other bikes. Everything is aligned and set properly as far as I can tell with plastic spacer bumps settling in the recessed dimples in the spacer plastic above and below. I worry about headset bearing longevity with this big of a gap. Everything else looks good otherwise at this point.