A very unexpected, but very welcome/cool blog post! I'm glad you're trying the progress system on a low-risk mechanic that still has good QoL improvements without (hopefully) cheese tactics. This system feels very natural and you don't have to go out of your way to really earn it, though I do like that you can be intentional about it and earn it faster if you want.
There are some interesting bread crumbs in all of this, namely, incentivizing colonies in multiple systems. While I don't think having a wider knowledge of slipstream patterns will be a decisive factor for whether or not I colonize a different system, this is a step in the right direction. I like the idea of claiming multiple sensor arrays having an effect on all colonies within a radius. Other similar mechanics could encourage spreading out more. Going "tall" (using a 4x term) of stacking all your colonies in one system for defense is a viable strategy but going "wide" should also have its perks.
Regarding slipstreams themselves: I like them when they work for me but I really dislike them when they don't. When the slipstreams are going in the opposite direction, there sometimes isn't any other recourse except to cross them and its frustrating when you're pulled off track so much. I wouldn't mind another hyperspace skill unlock that would allow "fording" of a slipstream. Sort of like a warp bubble that prevents slipstream effects for like 3 seconds with a cooldown of 10 seconds. Maybe it has a cost (Volatiles?) but E-burning through slipstreams can be very costly in supplies if you don't have the Industry skill. Alternatively, if you enter a slipstream at a near-perpendicular angle, the slipstream current doesn't kick in immediately (1 second?) The delay would allow you to cross narrow/fast slipstreams almost entirely without getting pulled in the wrong direction for 10 LY. Perhaps this feature is mutually exclusive with Sustained Burn.
(As a total aside, I will say it one more time: this progress bar system is going places, so I hope you're prepared to make another dozen iterations.

People are going to clamor for it to be used for Combat ("Combat XP!" "Split off Combat Skills from the main skill system!" "The more you fight the more Combat Skills you get!" etc), for Trade, for dealing with Factions, for campaign events, endgame scenarios...the list goes on and on. I think it has the potential to do some really cool things in the game, assuming of course, you want to spend the time on it!)