what is easiest way to make ram booting image from USB HDD?

I have made a very small w7 that started with winntsetup install to vhd then Wimbs compact vhd. I mounted that vhd with ImDisk and used Clondisk's filecopy feature to transfer it to a USB HDD so that I could boot on a couple of my systems and install the drivers including firadisk and WinVblock.

boots fine, everything works so I make a .raw image with qemu manager then format it with windows and copy everything over to it then defrag then unmount and add grub4dos entry:

title Ram Boot w7r.raw
find --set-root /w7r.raw
map ---mem /w7r.raw (hd0)
map --hook
find --set-root /bootmgr
chainloader /bootmgr


it boots but when loading it grub4dos shows info: total_sectors calculated from partition table (1092420) is less than number of sectors in the whole disk image (1136640)

thats a big difference (44220)

then after booting it it is out of space and not enough to load bginfo .tmp bitmap but I have 68mb free before booting in the .raw image. I dont know why this is happening or how to fix it.

I have always used this method with XP and the info message is only one sector off.

I need a good way to make a ram boot image from a working USB HDD. (How?)

problem is everything seems to want to make the image the same size as the partition and that is 10gb so that wont work for ram booting the image and I want to make the image as small as possible for fast loading.

how can I?

thanks