Honestly Shazza only you can make that decision and only you know what you can comfortably cope with.
Both my bubs were smallish (DS 6lb11 and DD 7lb) and DS was born by emergency CS after a long and extremely difficult labour - he was firmly stuck. DD was a forceps delivery as she was stuck as well but I was determined to have a vaginal birth. I have had considerable problems post birth (significant tearing and the world worst haemorroids adter pushing for 2 hours) and would I do the same again? I really don't know.
Having said all that I have a girlfriend who delivered her second son who by the way was 10lb vaginally without any problems at all, no stitches and a 4 hour labour.
If you want the CS then have it, it doesn't mean you have taken the easy way out and it doesn't diminish the significance of your fifth birth. Each and every baby takes a different path into this world. For some it's a vaginal arrival and with others it's via the side window!
Give it some quiet thought, you'll instictively know what it right for you both. xx