Suppose Knuth arrow notation (and hence the hyperoperation sequence) is extended to transfinite ordinal indices as follows:
Let μ be a large countable ordinal such that a fundamental sequence is assigned to every limit ordinal less than μ, and take these to be the same as in the definition of the fast-growing hierarchy of functions ($f_\alpha$). Now define
$$
m\uparrow^\alpha n \ \ = \ \
\begin{cases}
m n & \text{if }\alpha=0, \\
(m\uparrow^{\alpha-1})^n 1 & \text{if }\alpha \text{ is a successor ordinal}, \\
m\uparrow^{\alpha[n]}n & \text{if }\alpha \text{ is a limit ordinal},
\end{cases}
$$
for all integers $m, n \ge 0$ and ordinal $\alpha < \mu$, where $(\alpha[n])_{n=0,1,2,\dots}$ is the fundamental sequence for $\alpha$.
It can be shown that for all $\alpha < \omega$, there is an $n_0$ (depending on $\alpha$) such that for all $n > n_0$, $$f_\alpha(n) \ \ \lt \ \ 2\uparrow^\alpha n \ \ \le \ \ f_{\alpha+1}(n).\tag{*}$$
Question: Does (*) hold for all $\alpha < \mu$? Or, is there a "cross-over point", i.e., a least ordinal $\beta (< \mu)$ such that for all $\alpha \ge \beta, \ \ \ f_\alpha(n) > 2\uparrow^\alpha n \ $ for all sufficiently large $n$?
EDIT: Small cases $n = 0, 1, 2, 3, ...$ suggest that $\omega$ is actually the cross-over point. Proof?
Motivation: If (*) holds for all $\alpha < \mu$, it would seem that with minor adjustments virtually all of the points of interest concerning the fast-growing hierarchy ($f_\alpha)$ apply as well to the hierarchy of functions $(2\uparrow^\alpha)$.
NB: Arrow notation has been used for convenience. The discussion could be rephrased in terms of extending the hyperoperation sequence $H_\alpha(m,n)$, with a shift in the indexing to accomodate successor and addition.