I need double the power in an 8Ohm load than a UcD amplifier can produce. Is there some way I can bridge two, for example, UcD400’s?

To drive one of the modules 180 degrees out of phase, simply swap the negative and positive input signal wires. Connect the loudspeaker between both positive loudspeaker outputs of the amplifiers, and place a 100nF/200V capacitor across the loudspeaker terminals on the amplifier side. This setup is most suitable for 8-ohm loads, as each amplifier "sees" 4 ohms when an 8-ohm load is attached. A 4-ohm load may trigger the current protection, limiting the power output to less than expected.