I'm looking to add a secondhand DB to my 503CW. I've done a fair bit of research over the years, and think the most affordable option would be a good P30 - 45 or a Leaf. However, I have learnt that the older CFE lenses can struggle with the BACK's or visa-versa. My 503 CW is abut 4 years old and the 80mm 2.8CFE lens is about 11 years old, buts its super clean and works great. Am I being too prudent, or is this combination good to go?