I've uploaded a kernel with fixed refresh rate (60Hz) here: https://mega.co.nz/#!KRpGQRLS!aqlmYAPHnrkhJKHybQG8VWF0il7jp6H2b17WYrqj2hY
It's clocked to 1.6Ghz and is suitable for devices with power button issue.
Where did you source this kernel? 
He just have the sources, there are lot of people with the source available. Anyone can get them 
. Not funny if only one person has them. The more the better, and commiting to github if possible....
The JXD keymapper not working has an easy explanation. Most probably these new kernels use a different joystick driver which is dfifferent from the kernels used in old stock roms and webclaw's, and mapper and joystick driver are related to each other, Just check joystick driver name and most probably is different. Mapper is not an apk, it's just an activity enmbedded in framework. At least it is that way in GPD devices, and most probably in 7800B too. Though existing Tincore.....
Tried to PM you back skelton - however looks like you may have turned off PM'.s - board soft says you blocked me.
Anyway, to answer your questions:
It was a miscalculation in their math in rk-lcd.c for 66Hz. My guess is they messed it up when they tried to self-fix vsync issues (it was discussed in depth on another board).
For the HDMI bug it was in rk_hdmi - lines 45+ are commented out (no idea why). Also debugging was turned on - I'm not sure why. Driver from MK device was used (supports SiI9022A/9024A and ITE IT66121) and updated hooks in board file. Works perfects on my unit now.
64 HDMI_720x576i_100HZ_16_9, //45
65 HDMI_1920x1080i_120HZ,
66 HDMI_1280x720p_120HZ,
67 HDMI_720x480p_120HZ_4_3,
68 HDMI_720x480p_120HZ_16_9,
69 HDMI_720x480i_120HZ_4_3, //50
70 HDMI_720x480i_120HZ_16_9,
71 HDMI_720x576p_200HZ_4_3,
72 HDMI_720x576p_200HZ_16_9,
73 HDMI_720x576i_200HZ_4_3,
74 HDMI_720x576i_200HZ_16_9, //55
75 HDMI_720x480p_240HZ_4_3,
76 HDMI_720x480p_240HZ_16_9,
77 HDMI_720x480i_240HZ_4_3,
78 HDMI_720x480i_240HZ_16_9,
79 HDMI_1280x720p_24HZ, //60
80 HDMI_1280x720p_25HZ,
81 HDMI_1280x720p_30HZ,
82 HDMI_1920x1080p_120HZ,
83 HDMI_1920x1080p_100HZ,
I also agree with your last point, future releases will the bitmap updated.
@lujji - I agree, if this source is public we should all have access to it. I was not aware it was public (and I didn't want to piss of the person who provided it to me) hence my gumption to share.
Uploading to git...
Re: Keymapper issues;
JXD did update the driver in all 1.5 ROM release (the KK version shares this new version too). JXD referred to this change as a GUI update (this is why stealing the updated keymapper didn't work). As previously mentioned in my older post files in /framework must be changed.
