Display Signed Number in Base X

The following Redcode displays a signed number is a chosen number base:

dot     slt    @stack,    #1+CORESIZE/2
        sts.a  #45,       0
        slt    @stack,    #1+CORESIZE/2
        mul    #-1,       @stack
udot    mov.b  @stack,    <stack
        div.b  base,      >stack
        mod.b  base,      @stack
        slt    @stack,    #10
        add    #7,        @stack
        add    #48,       @stack
        add    #1,        udcount
        jmn    udot,      <stack
        add    #1,        stack
udloop  sts    >stack,    0
udcount djn    udloop,    #0

base    dat    10

Unfortunately, the code is pretty ugly. Can you suggest a more elegant solution?