This is a common problem when using Meshtool and exporting an obj file. If the mesh was exported in xzy format, it will be laying down with a few spikes coming up towards the hands.
To fix this problem without having to start over again, re-export the lying down mesh you have just created in the xzy format again. Then run meshtool using this new object file and the original gdmc. Import the new gdmc and your mesh should be standing up!
To prevent this problem in the future, be sure the 'XYZ' format is chosen when you first export your obj file.
longer form of the fix instructions:
Open up your mesh file with SimPE Go to step 29 and 30 in this tutorial
EXCEPT have the format where it says 'XYZ' use "XZY"
Save a new OBJ file (name it like bodyoopsfix or whatever)
now go to step 48 and open Meshtool
for button 1 read in bodyoopsfix (see 2 steps up)
button 2, the orginal gdmc
then button 3 and save your new GMDC with a name you can remember
continue on through the end, running SimPE and replacing the GMDC with the one you just saved.