I am a new player, and was originally string hopping. I hit a ceiling I couldnt push through and after searching youtube I stumbled upon Cracking the Code. I commited myself to using USX, at first I was even slower than with string hopping, except that quickly changed with practice, and I continue to see progress with a smoother, faster and more accurate USX picking motion. Except when Im trying to practice tremelo picking. After spending weeks of trying to tremelo pick in all sorts of different positions, I cant pass 150 while cleanly hitting notes or maintaining tempo. Unless I use a DSX. When I use the DSX, I can keep the same wrist motion, and I can go past 180 bpm with sixteenth notes (cant maintain it accurately, but with practice maybe could)… Ive been trying not to do that though, and instead force myself to just continue USX as it seems to make string changes a lot easier if I play notes in groups of 4. I dont know how I would use both fluidly, or if that even possible, and that if I practice DSX tremelo while use USX for everything else, im doing myself a disservice. Any advice on this is appreaciated.
This sounds like your motion is inefficient to me, 150bpm 16ths is too slow to be having issues with an efficient motion.
What! 180bpm 16ths is a really good tempo, exactly the kinda speed you should be aiming for, with practice you will be able to maintain this speed and should be able to surpass it 
Could you expand on this? If your talking about pentatonic sequences you can DSX-ify them with a little tweaking:
To me it sounds like your trying to use an inefficient motion rather than your efficient motion that with a little work will be good to go. You can continue down the USX rabbit hole but whatever your doing right now doesn’t sound like it’s working, this will require you to continue to experiment at higher speeds until you discover an efficient USX motion but why bother when you have a DSX motion good to go? 
The cool thing about DSX is that is almost related to DBX in a way, as most DBX players will naturally switch to DSX for faster phrases. If you eventually want to be able to alternate pick basically anything why not go down this route? USX is a great tool as well but I you develop a more distinctly single escape style of playing which is something to consider.
Anyway, hope that helps! My assessment could be completely wrong without an actual video of your playing though 
Hey, first off I really appreciate you taking the time to really consider and respond in length! Yeah with USX it didn’t feel natural at all to me at first. It still doesn’t, but it’s not nearly as awkward as it was.
If I can’t reliably hold 16ths at 150, then the movement I’m making is wrong you think?
So the reason I’ve been trying to force myself to get better at USX is for two reasons. 1. The escape is out of the strings on even amounts of notes hit thus allowing for more easily changing strings. 2. Also alot of what I’ve read is people saying USX facilitates muting the string with the picking hand more, which I can feel as well.
To be honest I haven’t really looked into playing DBX. I’m most interested in playing metal, so something that allows for smooth transitions with speed is a must. I’ll try out this DBX this week. Thanks again
Ah, so in that video you posted, he started with an upstroke (while using DSX) so that he ends up outside the strings in hitting the string even times. I will try this out.
Yeah 150bpm 16ths is too slow to be having speed issues with an efficient motion 
It just depends what you’re used to really, you use a slightly different part of your hand for DSX with an upward pickslant and with a zero-degree pickslant it is more similar to USX. For example, I believe Brendon Small uses DSX wrist and elbow for his metal playing:
Haha, I didn’t mean to send you down a DBX rabbit hole! I was just trying to sell some of the cool things about DSX! If your set on USX go for it but it sounds like you already have some tools to be a killer DSX player
Hey @khaight967 ! I can see you have a subscription, so I suggest you create a technique critique on the platform
Hey @khaight967 ! Welcome. This forum is awesome and full of great ressources. If you’ve got a subscription, the seminars are all worth checking out and could keep you busy for a long time. I still keep referring back to all of them regularly. I’ll echo @tommo and encourage you to create a Technique Critique. The teachers here are super cool, helpful, and insightful.
how do I create a technique critique?
Sorry for the delay! Here’s our help section for Technique Critique. These are all really short:
That should cover most of it. If you have any questions just email us in support and we’ll respond asap.
Just note that you need to complete the joint motion tests to unlock TC, but they’re pretty brief and the feedback they provide is invaluable:
I expect you will blow away your 150bpm number, and then you’ll have a reference point for why @Jacklr is saying 150 is probably too slow to be a meaningful benchmark for alternate picking.