Funnily enough you are the second person to mention about the hook flexing today Mark, never even considered it possible with smaller species before. I use a kamasan B983 pattern, which is certainly not a strong hook and so the action you describe could well be an issue. I do put a 6inch length of feeder gum on the hooklink to attach to the mainline though, so this should mitigate against the jagged head shakes somewhat. This addition has helped, but still getting more hook pull than I believe what you would class normal.
I tend to use a 6mm pellet on a long hooklink (2-4ft), as i've found this mainly produces a better stamp of fish for me than caster, maggots etc. and I don't have to worry about whether the bait has been mauled by minnows/small fish. The rod I use at the moment is a Tackle Box Darent Valley 11ft (0.75lb) Specialist Rod, and whilst not a tip rod, it has a pretty progressive action. Possibly not ideal though. I did switch from a Drennan series 7 specialist avon in 1.25, but this was far too heavy handed. Do you have any recommendations on a nice soft feeder rod that could do the job better? Don't mind getting a new setup if needs be if this is likely the issue.