Hung Ga and Wing Chun are "same system, different style". Meaning, both are "
Baan Jung Siu Lam Kyun", from Ching Dynasty-era Ming rebels who traveled on Red (Opera) Boats, both to plan, and to project their operations.
Now, whether one came from the other, or they were joined at that (or another) time, both have continued to evolve in close proximity with one another. Yes, each has its original focus, and each has evolved to become further specialized, as well. Meanwhile, each has already taken from the other what was initially important to be "complete" (to fulfill the purpose for which it was originally intended).
In the integration of any given skill or style, some analysis is called for. What is/ are the desired objective(s)?
For a seasoned practitioner of one style to become familiarized with the other, is to retrace the steps of how each style was built. Styles are designed with two purposes in mind a) to be efficient, and b) to neutralize all other martial arts. Note that while "a" will remain a constant, "b" will always change, depending on style history, and individual preference, in consideration of some pressing current need. Whether practicing a so-called "pure" style, or blending different systems, results are always better when we keep the desired objective firmly in mind.
Because of this,
any system/ style will reap great developmental benefit from spending time with any other system/ style. It's just a matter of asking, a) do I already have this? b) do I need this? c) do I need to learn to defend against this? d) will this be in conflict with my current approach? And even, e) will this be of any use to me at all?
As you are likely already well-aware, the best way to broach the topic of "cross-training" is to ask your Sifu if he knows the guy. If he is local, but Sifu has not already suggested it himself, there may be some "reason", therefore, one should certainly give all due consideration to his reply.
Anyway, if you decide to go ahead with it, please be sure to come back and share your findings with us here!
Best,
Michael