public static final Method setSize = ReflectionHelper.findMethod(Entity.class, "setSize", "func_70105_a", float.class, float.class);

    @SubscribeEvent
    public static void playerUpdate(TickEvent.PlayerTickEvent event)
    {
        EntityPlayer player = event.player;

        EntityEquipmentSlot head = EntityEquipmentSlot.HEAD;
        EntityEquipmentSlot chest = EntityEquipmentSlot.CHEST;
        EntityEquipmentSlot legs = EntityEquipmentSlot.LEGS;
        EntityEquipmentSlot feet = EntityEquipmentSlot.FEET;

        Item helmet = ModItems.SPACE_SUIT_HELMET;
        Item body = ModItems.SPACE_SUIT_CHEST;
        Item leggings = ModItems.SPACE_SUIT_LEGS;
        Item boots = ModItems.SPACE_SUIT_BOOTS;

        if(player.getItemStackFromSlot(head).getItem() == helmet &&
                player.getItemStackFromSlot(chest).getItem() == body &&
                player.getItemStackFromSlot(legs).getItem() == leggings &&
                player.getItemStackFromSlot(feet).getItem() == boots)
        {
            AxisAlignedBB aabb = player.getEntityBoundingBox();
            float height = 1.8F;
            float width = 0.6F;

            player.eyeHeight = height * 0.9F;
            player.stepHeight = height / 3F;
            player.setEntityBoundingBox(new AxisAlignedBB(aabb.minX, aabb.minY, aabb.minZ, aabb.minX + width,
                    aabb.minY + height, aabb.minZ + width));

            if(!player.world.collidesWithAnyBlock(aabb))
            {
                player.setEntityBoundingBox(new AxisAlignedBB(aabb.minX, aabb.minY, aabb.minZ, aabb.minX + width,
                        aabb.minY + height, aabb.minZ + width));

                try
                {
                    setSize.invoke(player, width, height);
                }
                catch (IllegalAccessException e)
                {
                    e.printStackTrace();
                }
                catch (IllegalArgumentException e)
                {
                    e.printStackTrace();
                }
                catch (InvocationTargetException e)
                {
                    e.printStackTrace();
                }
            }
        }
    }