[Roland777]

... and really gave some thought to what a sevenstring tuned in fifths would be like. And I came to the conclusion that it would kick ass!
Imagine having one tuned to F C G D A E B (Funny thing is, it's tuned exactly like a sevenstring bass... but backwards! That's a low F and a high B, right there). Of course, one would have to have a multiscale instrument to acommodate the vast differences in pitch ("28 to "25 - gauges 080 to 005, with the high B coming from Gary Goodman?) but apart from that, there shouldn't be any significant problems with the physical aspect of the guitar.
I mapped out the fretboard of this guitar and discovered the chording and riffing possibilities, not to mention the range - a sevenstring guitar tuned in fifths has more range than a nine-string guitar tuned in regular intervals!
I've come up with a couple of sketches which I'll upload at an appropriate time. Until then, feel free to discuss.

[dpm]

you've got to be capable of some serious left hand stretches for 5ths

[bostjan]

I used to have an idea for a multiscale bass with fifths on the higher strings to give it a symmetrical tuning like GCFCGD. That way the strings where you'd have to do stretches are closer to the edge of the fretboard, so they are more comfortable, and they are a tad shorter, too.

But with fifths, you can adapt chord fingerings to do some pretty wide range chords. Scales might be a bitch on the lower frets, though.

[Roland777]

Playing a 35" BTB555 certainly gives you more chops and stretch, I'll tell you. I don't think that a "28 scale would pose much of a problem compared to four note per string runs on a "35 scale.

EDIT: After going on a small trip to Soundland here in Germany, and checking out a lot of different guitars, I´ve come to three conclusions:
1. The indonesian RG7321's are NOT bad at all! Again, maybe I lucked out, but before you denounce these guitars, check one out! The one I tried was absolutely fabulously built. Then again, quality might go from guitar to guitar, so check one out.
2. I like ebony. A lot.
3. A "28 scale is no problem for four note per string-scales/-runs at all, atleast for me. I tested an Ibanez MMM1, and sure, you had to stretch a little bit extra, but that felt more like a cosmetical issue than a physical strain! Hooray for "28! Almost as long as something else.