You can only do so well on this level without the update. The update gives you 20 studs at the beginning of the level, which means you need to collect more studs rather than just focusing solely on the enemies. This will probably be the last WR done on 1.1.

Mod note: retimed Here I was able to improve upon my time by positioning myself at the top of the ramp instead of playing forwards at the bottom of it. This increases your FOV, allowing you to defeat the enemy units faster. You do, however, take more damage and collect less studs, but you can make up for this by abusing the shop's healing mechanic and getting studs by letting some units up the ramp before taking them out. I chose to only do this to speeders, because they drop a decent amount and they're fast enough that they generally reach you before you take out the rest of the enemies in the wave, netting 0 time loss. Try to combine your purchases with the heals for less overall shop clicks.

Here I also opted to use fullscreen mode, since it allows for more precision when you're tracking the enemies with your mouse, so it's harder to misclick. I think it also gives you higher FOV than normal, but I'm not 100% sure. This can also save you from clicking on a window behind the game and covering it up.