Man, the DS-1 ULTRA isn't a heavy metal tone maker ON ITS OWN... on its own, its good for like fat, fusion lead lines, or a classical rock crunch (with Seeing Eye mode).
Even when the boosted, you will not get a heavy metal tone ala a Metalzone or GT2. Why? Because the DS-1 wasn't meant to be a stand alone metal distortion unit.
I hear the tone of your Smarvo is pretty nice, good crunch.. stick to that for your rhythm tone... then use the DS-1 ULTRA to thicken to lead.
In addition, since you have a DOD fx100, you can do a 3 stage gain setup.
Gain stage 1 would be your amp alone, set to a lower gain.
Gain stage 2 would be DOD pedal pushing your amp to a more saturated distortion.
Gain stage 3 would be the DS-1 ULTRA either 1) thickening your tone (ULTRA mode) into a lead tone or 2) just upping your gain (Seeing eye mode) into a heavier tone
Note you got to start with a lower amp gain if you are using option 2 at gain stage 3, otherwise, expect noise.
I suggest using the DS-1 ULTRA as a tone thickening booster, so your lead tone is fat and nice. But thats my take on it...