Clocked Video Output slave control not functioning

Foram,

This sequence does not appear to work for me

Am I correct in assuming set functions start with 0? (i.e. 0 is mode 1?)

I defensively coded aiming for mode "2", just in case, so I won't care if it's the 2nd or 3rd in the sequence.

My process...

// 3 modes chosen as available in wizard
Clocked_Video_Output cvo(CLOCKED_VIDEO_OUT_BASE);
while (cvo.get_output_fifo_usedw() == 0) { }
cvo.clear_fifo_underflow();
// long pause
cvo.start(true);         //start cvo
cvo.set_valid(2, false); //set mode 3 invalid (or is it 2?)
cvo.configure(2);        //configure register settings for this mode
cvo.stop(true);          //stop cvo
cvo.set_valid(0, false); //set lower modes invalid
cvo.set_valid(1, false); //set lower modes invalid
cvo.set_valid(2, true); //set my mode valid
cvo.start(true);         //start cvo

VidModeMatch register returns 0.

Possible problem.

The reference design shows 18 registers per mode, but the VIP User Guide shows 19 registers. I tried it both ways. (At one point it was returning a 4 but I still don't know why) My own data dump of the registers indicates to me it's probably 18. Tons of 1s, followed by some garbage values. The 1s end where 18 registers per mode would end. (18*14+4 registers)

The test pattern generator is generating a 640x480 progressive signal, and I am putting in 640x480 progressive in cvo.configure().