Well did you have still SR enabled profile? Maybe you should disable SR and then go further than 900 MHz

sudo gainroot
kernel-config load dsp
kernel-config save mycfg

cd /home/user/.kernel
run-standalone.sh leafpad mycfg

Then change max frequency as you wish and change VDD1=1 and VDD2=1 to VDD1=0 and VDD2=0


You are right, only MyPaint and some emulators demand more than 900MHz for fluency...