I was using the ventilation, but I read that once you get to 100% it no longer works, even though it says the extra %.
With newest client version you can see that Improved Ventilation gives you % even after 100%. If you have 100% commander then rest of the crew gets 100% + 5% + 11% if you put mouse over the % and tooltop pops up. Since adding 10% into 105% it actually gives you 11% as commander bonus which is nice extra 1% giving you total of 116% as fully skilled crew with Improved Ventilation.
It is unknown if this gives you the % bonus after 110% but I would rather assume that it works same way as commander bonus. It would be nice to see the original post discalming this.
We tested view ranges and spotting in this post. While doing so we noticed that there was difference in range of 2 Leos detecting eachother. After analysing we derived that Improved Ventilation was the reason. This confirms that Improved Ventilation (+5% crew skill) works even when crew is at 100%.