Hi, welcome,
Do you have an audio demo of what you're trying to achieve?
Nick (The Girl Next Door) from the forums has programmed a whole bank of basses and they were fairly euro-oriented, with arp's and stuff.
Free for download either from his forum:
http://www.thegirlnextdoor.de/Virusforum.htm
or from Access' site:
http://access-music.de/support.php4
Vengeance (Manuel Schleis) actually made soundsets for the Virus before also moving on to other synths and doing recorded sample-sets.
http://www.vengeance-sound.com/eng/indexFLASH.html
The sub-oscillator is an extra waveform that's ALWAYS placed, I think, 2 octaves (-24 tones) below oscillator 1. You can't alter the pitch any other way in that aspect.
Tri waveform is similar to a sine wave, but just slightly more "plummy". Good for sub-basses where you want to feel it more than hear it.
Square is more hollow, good for making patches thicker and ballsy, adding more mid-low frequencies for a guttural effect. Or for making really evil D'n'B basslines.
There's not much else to tweak that aspect really. Whack up the sub oscillator volume, see which waveform (sq or tri) compliments the patch, and then decrease the sub level until it sits ok.
I think Euro-bass usually sounds cleaner though, stripped of really low freq's as they're left to a different sub-bass patch or similar.