I can certainly sympathize with your frustration. I've definitely had my share when it comes to doing I-Opener hacks. But so far I've managed to build 2 for myself and at least 4 others for friends and family.
Currently, all of the machines I've built are running very reliably with a K62+ at 450Mhz (4.5 * 100Mhz FSB) or similar.
In fact, I use one of them in my car as a navigation computer with a USB GPS device.
After reading your previous message, I'd say I have a few recommendation that I did not see in your list of mods.
In my experience the biggest contributor to getting an I-O to run reliablely is installing a fan (or 2) over the opening to the memory door. Without question, every I-O that I've worked on that was previously crashing many times a day is now stable because of this. Heat was killing them.
Please... throw some fans at it before the towel.
Also, to take advantage of widely available 12v fans, I use a 6v zener diode to tap off of the main 19v supply. However, I feed this through a 5v reed relay that is triggered off of the 5v line of the serial port. This allows the fans to turn off when the power is turned.
If you need more info on this let me know.
The next critical mod is the widely mentioned, extra current boost from adding the .012 ohm SMT resistor on top of R302.
Also, put a .13 ohm 10 watt cooling resistor at the OUTPUT of Q16. This too can be cooled nicely by the fan/s on the memory door.
My next challenge. I have installed Windows XP on my car navigation I-O so I can take advantage of "Hibernation". It works very well now, and reliably, however it took several days for me to get it installed because it was crashing quite consistently at first.
I finally found that the 100Mhz FSB was the problem - even though this exact same I-O had been running PERFECTLY for months under Win98se. It seems Win XP would only install and run with 66Mhz FSB!!! That plus a 6x multiplier gives me 400Mhz CPU speed.
I'd still like to bump it back up to 450Mhz if possible.
If anyone else has the answer to this could you please post it??
Good luck Gramster.