Well I use this code snippet (replace HUD_1 with whatever name you've called your hud);
;RESCALE HUD TO CURRENT SCREEN RES
HUD_SetScale ( HUD_1, Float(GraphicsWidth())/640,Float(GraphicsHeight())/480 )
HUD_Position (HUD_1, -HUD_GetX ( HUD_1 ) , -HUD_GetY (HUD_1 ) )
HUD_Update()
;RESCALE HUD TO CURRENT SCREEN RES
HUD_SetScale ( HUD_1, Float(GraphicsWidth())/640,Float(GraphicsHeight())/480 )
HUD_Position (HUD_1, -HUD_GetX ( HUD_1 ) , -HUD_GetY (HUD_1 ) )
HUD_Update()