Yes, you're right, ring lands will only blow if the pistons get too hot or there is detonation.

Turbo kits have been blowing ring lands on this board since the day they came out. Do a search of the turbo forum for "ring lands" or "compression" or "blown" and you'll see that most everyone with 420a turbos blow their piston ring lands at one point or another.

In my case, these factors contributed to blowing my engine at 6psi:

HRC FPR: Defective (by design) Fuel pressure fluctuated by as much as 20 psi between starts.
EGT Gauge: Missing. HRC kit doesn't include one.
Stock Injectors: Inadequate. They "can" be forced to work by running them way outside their spec. One of mine jammed.
HRC Fuel gauge: Defective. Not HRC's fault.
HRC Boost gauge: Defective. Not HRC's fault.

Not all HRC kits have all these problems, I got unlucky to a certain degree. If HRC would replace the Cartech FPR with the Vortech SFMU, and require bigger injectors for Stage2 and above... we'd have a nearly perfect turbo system. However, Bill insists on using the cheaper Cartech unit, and relying on the factory injectors to function at 110psi instead of the 43psi they were designed for.

If you're building a custom turbo setup, post all the fuel components you're using.

You can search the archives, but the basic necessities for 5-10psi are:
SFMU, 310-440cc injectors, Missing Link, intercooler, EGT gauge, a/f gauge or datalogger, boost gauge, high pressure+high volume fuel pump, and a fund for a rebuild kit. I've seen turbokits work on 2gnt's with 160,000 miles no problem, its just all a matter of whether your fuel system works right. Our stock bottom end can handle about 12psi on 93 octane or 10psi on 91 octane forever as long as the fuel system works.