Wouldn't a quick, dirty way of looking at the 7th Amendment would be to:
1) Look to the Federal Rules of Civil Procedure, since the 7th Amendment would only apply to the federal courts.
2) Trust the FRCP as gospel since the (legal) gods themselves gave it to us (they're written by the SC, who are the arbiters of what's what and how to interpret the Constitution).
3) Look to FRCP Rule 38.
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What I'm saying is that:
1) the $20 dollar limiation was just placed there to ensure it was a controversy of some substance and not frivolous/whimsical. So the way it's interpreted today is that it's not literal and subject to period changes.
2) unless you're looking to mount a Constitutional attack on some matter, revisiting 7A would probably be less meaning full relative to just heading off to a FRCP vs. Article III courts analysis (but see next point).
3) since the SC writes the rules, and since the SC interprets the Constitution, you're rather limited in forums for an argument mounting a 7A attack based on the $20 limit, making the point kind of moot if it is expressly limited to the $20 issue.
4) My beliefs as to strict original interpretation is that it shouldn't be so. You'd be left with a document relevant only to the circumstances surrounding its drafting or at most any potention foreseeable situation. Since I believe that foreseeability decays exponentially relative to the temporal distance you're looking out ahead, you'd be left with a document that becomes obsolete too fast. I believe rewriting laws everytime situations change would undermine one of the reasons laws exist in a common law society -- which is to lend to predictability and stability. You would end up with a very incoherent amalgamation wherein every statute would be argued over it's relevancy each time the matter came up. After having dealt with matters in a civil code society before, I am pretty much against the daily (and what seems to be whimsical) interpretations that are handed out with each time an issue comes to the bar, which is what a strict original interpretation / re-write the code as necessary approach seems to lead me.
I'm not sure if my argument made that much coherent sense itself, but it's really hard to type on the fly in this little 2 inch wide gray box where I can see only a few lines of text at a time. Basically I'm saying that in my opinion, strict original interpretations don't work as you lose relevancy rapidly.