John,
As a Skier of the southern Cascades heavy dense snow is about all we get, most of the time. I joke that they don't have real snow in Utah or Colorado it is full of air. They don't know what real snow is.
I'm not sure what kind of heavy snow you are talking about. Heavy bottomless or heavy snow on top of a base. I'm going to assume you're talking about heavy on top of a base. Because until you can handle that, your probably not going to try bottomless.
First of all regarding an ACL injury, getting back on your skis is more likely to cause you and ACL injury than going head first. Read the information at this site, to understand the risks of getting back.
http://www.vermontskisafety.com/kneefriendly.php Unfortunately I have first hand experience with this.
As far as skiing heavy snow the two main differences are that you are constantly decelerating and wanting to be pitched forward and it wants to pull your feet apart. So to deal with the deceleration and wanting to be pitched forward it is imperative that you have a strong core. So hopefully you have been doing your abdominal and lateral crunches and back extensions. Focus on keeping your feet pulled back. This will co-contract the muscle both fore and aft and help to stabilize your upper body. Ideally, you then have what I refer to as a dynamic tension, that is both stable and flexible and allow you to go through clumps of snow without getting pitched forward too much. If I am skiing in my Head Raptor boots, which are stiff, I unbuckle my top two buckles and use just the BOOSTER strap to hold the liner of my boot to the cuff of the boot.
http://www.boosterstrap.eu/english/booster.aspThis lets the ski ride up over the irregularities, your ankle to flex more without pressuring the tip and smooths the ride out. If I am using my Alpine Touring boots I don't need to do this, they are already flexible. You will be amazed at how much you can flex forward without your skis diving, by doing this. Kind of like Dick Durrance skiing powder. (Google images of him, I think his Dipsy Doodle was the first retraction turn). This will tire your quads out and takes more strength, but I find it worth the trade off. I like to warm up skiing, with my boots unbuckled and the booster strap loose. It makes me more sensitive to being right on top of my feet, first thing and it is a great work out for the quads.
In regards to the snow wanting to separate your feet, it is helpful to do adduction and abduction exercises, to make sure you have sufficient strength to help hold your free foot in. I focus on keeping my feet together and not letting snow get between them and when it does pulling them back together. This is covered in the PMTS material, look at the Phantom Drag exercises also.
The last thing I focus on when the snow is heavy, is counteracting earlier in the turn. After I touch my pole, relax my stance leg and raise my inside shoulder (see ACBAES 2 book page 118), I also add, exaggerating raising my inside hip and letting it drop into the new turn. Everybody seems to have a tendency to project or rotate their hip into the turn when the snow gets heavy, or hard to turn in. By focusing on this, it eliminates or reduces the tendency for me to rotate into the turn and put me off balance.
I hope you have fun in the heavy snow. It is great for improving your skiing, it will exaggerate any mistakes in your skiing. When you have all the Essentials working, it is more fun than the groomed, in my opinion and it is easier on my arthritic hips and back. And often I have an entire run to myself, because nobody else wants to ski it.
Kirt