As I've been gradually applying more rules (as I grok them), Drake et al
decided to skim themselves some "cheap fuel". Dice karma and hilarity
ensued.

After limping through Jump and into Prometheus Highport, Nikki had to
spend four weeks in drydock stripping the _Paradise_'s compromised
armour shell, untwisting the aft frames, spending approx 500k solars
chasing up new armour, and then fitting same.  As opposed to 20k solars
for a load of refined fuel.

Further reading through the rules in question (sustained-damage crits,
and GG skimming) lead me to the question in the topic.  Does PC
overconfidence + small ship necessarily massively elevate risk of neat
burial in J. Random Gas Giant?

Is this me overthinking things, me misinterpreting the rules (a distinct
possibility), Mongoose's love of thinking thru
implications/interactions, or something else?

Sustained-damage critical:

MGT2 Core, p158:

"A ship will suffer a severity 1 critical hit every time it loses 10%
(rounded up) of its starting hull (points)."

GG skimming:

MGT2 Companion, p 156:

"Crossing from one layer to another, up or down, requires an Average
(8+) Pilot check with the largest negative DM for depth applied. Success
indicates the ship has successfully crossed to the new layer without
much more than some buffeting. In the event of failure, the ship fails
to cross the layer and is bounced back with considerable violence. A
second Pilot check, this one at Difficult (10+) difficulty and subject
to the DM for the layer the ship is currently in, is required to avoid
damage. If this check is failed, the ship suffers a number of dice in
damage equal to the number of the layer it is trying to enter. So, a
ship trying to enter the Deep layer and failing, suffers 4D Hull damage
unless the pilot can succeed the second check."

For some concrete examples:

A stock 200 dton ship (such as the _Butchers' Paradise_ ) has 80 hull
points, thus it would endure a severity 1 critical every 8 points of
hull damage.  100 dton ships have half those totals.

A stock 1000 dton ship (such as the container freighter _Astral
Venture_) has 400 hull points, etc

A stock 5000 dton ship (such as the mobile depot ship _Gadget
Hackwrench_) has 1,000 hull points, etc

Up towards the higher end, a stock 25,000 dton ship (such as the light
battleship TCS _Wubbo Ockels_) has 12,500 hull points, etc.

The Extreme Shallows are the highest layer with enough fuel to be worth
skimming (at 10% of full rate), and cause 2D6 buffeting damage when the
pilot messes up.  Assuming two points of armour and said armour applies,
the hapless hundred-ton ship has a ~70% chance of copping a
sustained-damage critical, assuming no existing damage.  The _Paradise_
would have a 16% chance of copping a sustained-damage crit straight up. 
The bigger ships would point and laugh.

The Shallows pentuple skim rate (to 50% of full rate), but causes 3D6
buffeting damage.  That would give the _Paradise_ a 62% chance of a
straight-up sustained-damage crit, and 91% for the hapless
hundred-tonner (which would include a 62% chance of 2+ sustained-damage
crits in that 91% chance).  Again, the bigger ships aren't too concerned
(although the _Astral Venture_'s captain may wonder why she was trying
to skim in the first place).

Is the sustained damage critical automagically applied to the hull, or
is it rolled anew like a combat hit?

If it's automagic, it might well end up uber tragic for the hapless
hundred-tonner - I would tend to not apply armour to hull damage caused
by crits.  A sev 1 hull crit on a 100 dton ship has even chances of
inflicting _another_ sustained damage critical - in the automagic case,
that ups the sev 1 hull hit to a sev 2 hull hit.  2D6 _more_ damage has
a 90-odd % chance of inflicting _another_ hull crit, as the Spiral O'
Clobbering almost certainly continues until the hapless ship breaks up.

Having typed that out, I now really don't like the automagic case.

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