| One thing to note is that any time you use the boost channel of the Hematoma you will alter the gain structure of everything else after it. You can dial everything in perfectly, then step on that boost switch, and it all goes to hell. The way to use that boost well/properly is to put the Hematoma last, and use an amp which overdrives nicely when fed a hot signal. Or if you have a pedal which acts like an amp for overdrive purposes, you can put that after the Hematoma.
Aside from the boost channel, the Hematoma doesn't introduce any dynamic spikes on its own. So there's no need to compress it. Flangers often do have big gain spikes and dips at certain frequency points, so they can benefit from compression.
Try using the Demeter by itself first (well, with the bass and amp). Start with the knobs on the Demeter set to around 12:00, and see if you can dial in a comfortable amount of compression from there. If it still squashes the heck out of your signal, even with the comp knob turned down around 9:00 or so, then try adjusting the trim pot.
Once you have it set up well for your bass, then add the flanger. You may find that it needs a bit more compression, or maybe not. It's a balancing act. If the flanger is like ridiculously louder than the plain bass signal, then you may want to look at ways of reducing the output of the flanger other than using the Demeter. | 
