[Q] Brick Fire HD 7 black screen after root topic

I rooted a friends HD 7 unit and loaded the img and twrp for the HD 8.9 by accident. Was told that it was a second gen however found out unit is really 43Z60 which is 1st gen HD 7". Did the following:

adb push stack /data/local/tmp/
adb shell
su
dd if=/data/local/tmp/stack of=/dev/block/platform/omap/omap_hsmmc.1/by-name/system bs=6519488 seek=1
mount -o remount,rw ext4 /system
mv /system/etc/install-recovery.sh /system/etc/install-recovery.sh.bak
mount -o remount,ro ext4 /system
reboot bootloader

Unit OK after reboot to this point. Then did the following:

fastboot -i 0x1949 flash boot kfhd8-freedom-boot-8.4.3.img
fastboot -i 0x1949 flash recovery kfhd8-twrp-2.6.0.0-recovery.img
fastboot -i 0x1949 reboot

After this fastboot reboot the unit is now black and will not give any logo or power on. Tried the 20-30 sec power switch and running fastboot -i 0x1949 getver but no change. Device does not show up in device manager. Read some other posts that purchasing a fastboot cable may be able to recover it. Do you think that will help or am I screwed at this point? Should I try another method of recovery?

PLEASE HELP! Any comments appreciated. Otherwise off to Ebay to buy a used unit! :(