Engines need the advance they need.  More advance than optimum is not "better" nor do you want to make changes to allow more advance than needed. For example, running super high octane fuel to keep it from detonating with more timing advance than needed for most power is going to give you less power, not more.

Two strokes simply need less advance, especially as rpm goes up.  Modifying the squish properly should result in a need for even less timing advance. 

You could try to retard the static timing to where total timing at 3,500 rpm is about 25 to 30 degrees...  it should run pretty good like that as long as it retards pretty quickly after 3,500. 

Yes Mark, I'm aware of and agree with the points you make, perhaps only that my understanding is that improved squish parameters tend to reduce the tendency to detonate, so perhaps will tolerate more advance, but usually actually"need" less.
The problem I'm having is the "advance" range of the CDI I believe is to great. To set the maximum to around 24 deg as I'd like @ 3 - 3,500, it will be 14 degrees at 1,100.
As a good deal of our riding is tight technical single track, 2 -3,500, the engine will spend a lot of time in a too far retarded range.
It might also be noted, I like to keep the revs low, not interested in wringing this bike's neck. I ride a WR300 Husky for that.
So, I'm interested to hear if anyone has managed to get  a Rex's RMK9 Dual Power Full Race CDi ignition to work on a DT360A ?

I'm running the full race kit.  I have not attempted to map the advance curve or even verify if it is working as advertised but the bike runs very well.  It pulls strongly from idle on up.  Low-mid power is quite good.  All of the other engine work plays a large part in this of course, the stock DT360 is miserably anemic in the low-mid part of the power curve despite it's conservative port timing and large displacement.  The most effective fixes for this require porting among other things.  Its a 351cc two stroke, the potential is in there. 

14 degrees at 1100 doesn't sound inappropriate to me.  If it is a straight line ramp upward toward 3500 you're looking at 19 degrees at 2300 RPM and 21.5 at 2900 RPM.  That should work if you get the rest of the motor sorted out.