Multiple render targets exception

Wrong behavior - error, illogical limitation:
While opening more than 4 render targets at same time I am getting exception:

Destination array was not long enough. Check destIndex and length, and the array’s lower bounds.

One of advantage of shader model 4.0+ is ability to render into more than 4 outputs at same time. This is killing possibilities quite a lot and in my case it force to use twice as many drawcalls than it would be needed otherwise.

Any ETA on fix or is there way how I could fix it myself? (not sure how many underlying issues there can be.)

About fixing it myself for now:

Line 53, start from there.

Then fix render target clearing…

Am I missing something?