The Rockstah mod 5 is really a one trick pony VH mod which was Marks goal. I installed one according to those schematics and it was Blah sounding quite honestly. I made some changes and got it sounding pretty good as long as you have the chops but it was kind of uninspiring to play it just didn't have that plexi about to explode qualities to it.
I would have to say the best plexi style mod out there IMO is the Michael RT/mod which still retains plexi feel and tone with alot of gain... more gain than the Mod 5. I have done a mod similar to the RT/mod to my 72SL and I like it alot better than the mod 5.
I think the Bray is also a good proven great sounding high gain plexi mod if modded plexi tones is your goal.
Here is some clips of my mod 5 in a 50 watt plexi amp which I eventually went with a Cameron inspired JCM800 for that amp but it was no longer plexish IMO. These clips were straight into the amp GB speakers 12K SD pickup fairly low/medium volume.