The "FLASHER_v2.15_ADB_FOR_U30GT2.rar" package on this Russian/Ukrainian forum has a folder ("IMG") that seems to be a repository of kernel images (about 15 of them). This is where I got the overclocked kernel #38 that I created a CWM-based installation package for. Since I can't read Russian or Ukrainian, I have no idea who packaged these things, although someone called ImaSoft has claimed responsibility for the overclocked kernel #38 image posted elsewhere in this forum.

I have created CWM-based installation packages for each of the kernel images, plus a separate package for the stock v2.06 kernel. This way, people can install and test individual kernels (instead of complete ROMs) from CWM Recovery.

Of course, testing different kernels may turn out to be a pointless exercise - and there is always a risk that a particular kernel will not boot at all (or worse) - so you'd better be sure you can boot your tablet to CWM by pressing the power and volume + buttons before trying anything. I myself will NOT test any of the kernels, so anyone testing any of them will be on his own.

Anyway, here are the repositories:

A. Several iterations of Kernel #38, stock, overclocked CPU, GPU, DDR, in various combinations:

http://www.arctablet.com/users/forum/kernel38_CWM_repository.zip

B. Kernels from the Flasher 2.15 package:

http://www.arctablet.com/users/forum/CWM_kernel_repository.zip

README:

1. The kernels in the "kernel38_CWM_repository.zip" file are based on the stock kernel #38, with various patches applied. The names of the individual files will provide a clue as to which part is stock, and which parts (if any) have been overclocked.

2. The kernels in the "CWM_kernel_repository.zip" file were downloaded from a Russian/Ukrainian forum (http://4pda.ru/forum/index.php?showtopic=458533&st=300#entry22299125). They are in the "FLASHER 2.15" archive on that forum. They have been extracted from the archive and a CWM-based zip installer has been created for each of them. The ones with "OC" in their zip file name contain overclocked kernels (or, at least, that is what I think).

3. These kernels have NOT been tested (certainly not by me). If you are feeling very brave, then you can test one or more of them on your tablet. If in doubt, don't try any of them.

4. As with any low level stuff, flashing kernels and firmwares is not for the faint-hearted. Things can go badly wrong at any time, and without any warning. And there is always a risk that a particular kernel will not boot at all (or worse) and so you'd better be sure you can boot your tablet to CWM by pressing the power and volume+ buttons before trying anything. Otherwise, it's back to the Rockchip batch tool to install a full ROM!

I am not the author of any of these kernels. I cannot answer ANY question about the functionality or operation of any of these kernels - so do not ask. I will simply ignore all such questions.

NOTE:
Kernel "0012_Wed_Oct16_11.48.35_CST_2013" seems to be the stock Cube kernel for firmware v2.06 (and the Kasty 20131029 ROM). There is an "OC" (overclocked) version of it.

DISCLAIMER:
You use these zip files or anything in them entirely at your own risk. If your tablet is bricked, then that is just too sad. If you are worried about bricking your tablet, then  STOP RIGHT NOW!

To install any of the kernels in these packages you must have CWM Recovery installed on your tablet, and you must have a Kasty v2.04 or 2.06 ROM for Cube U30GT2 from this forum.

Installation:
* Extract the contents of the desired repository.zip archive to a temporary directory.

* Then go to the temporary directory and select the specific "kernel" zip file that you want to flash.

* Then take the following steps;

0.  Remove any *external* SD card
1.  Copy the relevant kernel zip file to the tablet's *internal* SD card (NAND)
2.  Reboot the tablet to CWM Recovery
3.  Select "Install zip from sdcard"
4.  Then select "Choose zip from sdcard"
5.  Scroll on the SD card to the kernel zip file, and select it
6.  Confirm that you do want to install it
7.  The tablet will reboot back to the CWM Recovery
8.  Select "Reboot system now"
9.  Wait for 5 minutes after rebooting, and, hopefully, all will be well.