I didn't use 3dgs for years but what does your

printf("%d", v);

say?

Don't you have the variable "v" as a string to the panel string instead of writing it as char into the string? I guess it just interpret it as the char "v" which won't work and deliver 0?

I dunno how you can combine strings now in 3dgs but it's probably supposed to be something like this:

PANEL *mypanel = pan_create( "bmap=mybullet; flags=VISIBLE | OVERLAY; pos_y = 130; pos_x = " + v + ";", 11);