A tail emissions rate of 0.03% or less annually seems acceptable.

    #!/usr/bin/env raku
    use v6;

    multi sub inflate($n, $r, $y)
    {
        my $m = $n;
        loop (my $i = 0; $i < $y; $i++)
        {
            $m = inflate($m, $r);
        }
        $m;
    }

    multi sub inflate($n, $r)
    {
        $n * (1 - $r);
    }

    sub MAIN(:$rate = 0.0003, :$years = 100)
    {
        my $purchasing-power = 1;
        my $inflate = inflate($purchasing-power, $rate, $years);
        my $output = qq:to/EOF/.trim;
        After $years years of inflation at a rate of {$rate * 100}% per year,
        purchasing power is {$inflate * 100}% of what it was initially.
        EOF
        $output.say;
    }

All else equal, a 1% annual rate of inflation costs you over half of your purchasing power per century. Even a 0.1% yearly inflation rate charted out over several centuries results in a collapse of purchasing power. This level of inflation practically requires investors to take countermeasures, like searching for alternative stores of value...

Expanding the supply on demand through on-chain governance in a way stakers can profit from, while sacrilege to “digital gold”, would be more palatable to me than rates of tail emission higher than 0.03% or so.

is 0.03% enough incentive to secure a trustless network?

I’m only commenting from the perspective of investors concerned over debasement. 0.03% annual inflation reduces purchasing power by about 7% every 250 years.