Hi keno,Bongy;
Have you tried raising the current level to 1.5amps, which is the new rating that CREE recommends? It would be interesting to see the difference between .98amps and the 1.5amp level.
How long is the cable for the sensor on the PAR meter? I would need the cable to be around 33 inches to work in my 200 gallon.
The cable for my unit is about 80 inches, should be good enough for your 200g.
You are correct that XPG can take a max of 1.5A. However, I don't have any parts available to drive it at this current yet. 1A is really the max I can find.
Also, the efficiency drops as current is increased. From CREE's graph, increasing from 1A to 1.5A will increase flux by about 1.3 to 1.4. However, you will need to deal with additional temperature.