Is there any progress on a “baby $abc$ conjecture” where you restrict attention to rational approximations of $n$-th roots?

Let $r/s$ be a very close approximation to $(t/u)^{1/n}$, so that 
$$
|u\cdot r^n - t\cdot s^n| = a
$$
is small.  We thus have a pseudo-$abc$-triple with $c$ being the larger of $u\cdot r^n$ and $t\cdot s^n$, and $q=\frac{\log c}{\log(arstu)}$.

**Example**: the fifth root of $109$ is very close to $23/9$, so we get
$$
2+109\cdot 9^5=23^5,\quad 5\log(23)/\log(45126) = 1.4628,
$$ not quite as good as the $1.6299$ it gets as an $abc$ triple where you use that $9 = 3^2$ but still good enough to make it the “best” known approximation of any root.

Is anything known about $q$ in terms of $n$?