So the question is: outside of the cost is there a downside to a newbie with a HP100?
Is there a downside to an HP 100? Maybe...
At the beginning of the dive, they are about 10# negative - 8# of it as air. You adjust your weights for the empty condition so you are definitely 7# or more heavy at the start of the dive.
Now, if you immediately go to depth and your wetsuit compresses, you lose that buoyancy and you are even heavier.
Perhaps you are using a SS backplate and maybe even backplate weights. These are non-ditchable.
So, you could find yourself on the bottom with a completely failed BC and a full tank. Even after ditching your weights, you still might not be able to swim yourself off the bottom depending on your equipment configuration. Backplate weights might be a really bad idea!
Over in the BC's subforum, you can find an Excel spreadsheet that deals with buoyancy. Fill in some typical values and see how much weight you will have to swim off the bottom even given that you have ditched your weightbelt. It would be cell F17 - cell H21; depth1 total minus Need lead.
I used:
Head weight = -10
Tank full = -10
Tank empty = -2
Suit = 24 and 8 {the suit is 24# positive at the surface and 8# positive at depth - a WILD guess}
BP = -8
Light = 0
Doubles = 0
Integrated = 0
This results in depth1.total = -24 and Need lead = -14. So, if I ditch my weights, I have to swim 10# off the bottom. Beats me... But if I had 8# of backplate weights and only 6# on my belt, I would have to swim 18# off the bottom. Gee, I kind of doubt it...
The problem is somewhat worse for the HP 130.
I have been deeply interested in this problem as I have HP 100s and I'm getting really old. I don't plan on doing any deep dives but if I ever do, one thing I will try is swimming off the bottom with an empty BC, full tank and no weights. Maybe I'll put a 20' tether on the weights and leave them on the bottom. This way when I go up a ways and after the wetsuit starts to expand, I will be able to stop the ascent.
I never consider by buddy to be my backup plan.
Richard