Thanks for posting and being brave enough to ask for opinions. Before we get to technique, thanks also for the postcard shot
Don't let anyone rag on this. It captures what is fun about skiing.
There are some fundamental things we can point out.
Here you are leaning into the hill. As you turn across the fall line, you want your shoulders parallel to the fall line (in this case your right shoulder lower than the left). The other thing that we want to see happening at the end of your turns is that your upper body faces more down the hill then your skis. Here your hips and shoulders are facing your ski tips. You are also cutting way too much across the trail and finishing the turns with a skid to an edge set to control speed.
In general you have your weight too far back. But when you control speed at the bottom of the turn, you are going to overflex at the waist because your legs/knees are unable to absorb the sudden decrease in speed. See how much of the inside ski tip is airborne? The snow is not that deep. It's up because you are going over a mogul. Some amount of air is unavoidable. The question here is are you in a position to drive that ski tip back onto the snow ASAP? Here, the answer is "no". If you draw vertical lines from the toe and heel pieces, you want to see most of your body mass in between the toe and heel piece lines most of the time.
When you have your weight too far back, guiding the new turn with the inside ski is difficult. So you need to lift it to get it out of the wayyyyyyy. BTW - Here you can see most of your body mass behind the "heel" line.
This is what we call overflexing at the waist.
What could possibly be wrong with Duke's alignment? Would you care to elaborate?
Let's recap. Steep crud without stopping or crashing. Pretty good. Sore back? Eventually!
Crud tends to revert "good technique" to "old habits". It's real hard to fix fundamental technique issues in crud when you have the same issues on groomed snow. We don't know if you have these issues on gentler terrain/easier snow. If you don't then the thing to do is to go back to easier terrain and become more aware of the fundamentals I've pointed out (shoulders parallel to the slope pitch, developing counter through turn finish, keeping the weight more centered, control speed through round turn shape vs skidding), then carry that awareness back into more difficult conditions. If you do have these issues in your normal skiing, these problems tend to feed off each other. In this case we would need more investigation to determine the root cause (e.g. an alignment issue like knock knees).
Stay more in the fall line (vs turning so far across the hill)
Let your whole body flow across the skis as they cut underneath you (vs collapsing at the waist)
Close your ankle joints (lift the toes) to get the skis to float in the crud (vs sitting back)
Aggressively drive the ski tips back to snow contact on the back sides of the moguls
In softer snow you want to balance against the outside ski less than on firmer snow (but more than we see in this clip). You also want to keep your skis a little closer together (both tip lead and stance width) to get them to act more like one unit than two independent ones. With these changes and more upper/lower body separation with the upper body staying more vertical, you will be better able to resist the snow knocking you around so much.