It's possible to place a portal on the ceiling as you enter the chamber. It is also possible to request the cube from the upper button (which you meet before going down) then quickly reach down to place the portal for the cube, with barely enough time. Since you already had the ceiling portal ready, you just have to make it there fast enough to place the markboard portal for the cube. After the cube enters you can prepare the strafe jump without making new portals, and finish the mission quickly.

My previous pb was 1:27:06. I did get a slightly better run afterwards and beat this pb, but haven't uploaded it yet (1:26:42). Both were scuffed runs with reloads and mistakes.

Yes. You are correct CynicalA, it is actually possible to do it bridgeless. You need a sick strafe jump though but you can also have the ceiling portal placed. Sounded crazy at first but i just tried it and it worked on the second attempt. Holy cow. I suppose one could even want to skip placing the ceiling portal before the jump but it sounds too hard. Will give it a shot, see if it's possible... and it is (edited).

Edit: Erased the original message where i didn't believe there is enough velocity. Edit2: Actually possible to go bridgeless and without any portals set up. You throw both portals while midair. Too risky though. Edit3: Video of bridgeless attempts. w/ and w/o portal setup.

I am trying to speedrun this game and i found out two really interesting solutions/ tricks that could potentially save a good amount of time. One of them is way easier and more effective than the other but it feels like both are really interesting in their own manner.

Easy one - Chapter 6 - Conversion Gel Climb - "1 Building Solution" - In this solution the test subject doesn't have to get on the second building and thus saves a lot of time compared to the alternatives. Two points to mention. To get up on the first roof use two VERTICAL portals for an easy angle. Also when on top of the roof you have to place the roof portal as shown in the video otherwise you might not have enough airtime to reach the platform easily. Video below.

Hard one - Chapter 6 - Vacuum Tube Examination (part2) - "Midair Gambit" - In this solution the test subject has to implement acrobatics and precision in order to skip using the faith plate to get launched inside the tube room. This is a hard trickshot and personally i am not consistent in pulling it off. Made a single level video though to share it here and see what other players think about it. If done properly it finishes the mission in a heartbeat. On the flip side, just 2-3 failed attempts could easily result in a time loss instead. Video below (trickshot shown around ~0:57).