californiagrownYes, there are certainly those times, but at 6'4" and 200lbs what can you expect?! Any suggestions to mcguiver the boot?
The Achilles issue is the worst problem. It's more of a bad pinch/bruise/trauma issue. Why is that happening? I'm an engineer and like to know the cause before figuring out a solution.
Making that specific boot stiffer is going to be difficult because there are already 2(?) screws in the back. If there's only one, you can drill a hole and add another and it will boost the flex by about 10 points. But the bigger problem is the soft plastic over the instep- as you flex forward, it will collapse and there's nothing you can really do to stop it. On their RX/RS models, that piece is absent which yields a more structurally sound shell design. But, those models are also narrower & lower volume...
Your Achilles problem is most likely due to/associated with your limited dorsiflexion. If your boot allows you to flex more than your biomechanics allow (especially during those singular, hard "bottom outs"), then it will strain your Achilles for sure and lead to pain/swelling in the area you described. I hate to say it, but finding a boot that has a similar geometry (upright stance of 12° or 13°) but a more stable shell will help you a lot. But nonetheless it would be a good idea to see a PT in order to help heal that area before it gets worse.
You could also look into getting a firm Intuition Power Wrap liner. This liner style will help keep you more upright (nice, thick padding in front of the shin) and because they use very firm foam, it will help keep the shell a bit more stable than you current liner. This will be easy to test in the shop for you at least too.