Steve,
You'll get loads of opinions on this one !
Is 5ozs excessive ? Hmmmmmmmmm for most rivers, in what is accepted as 'Summer Flows' then probably yes !
Some people will tell you that they can hold bottom on a flooded river with 2ozs ! Well, fair play to them ! I've never been able to manage it !
On certain stretches of rivers such as The Wye or Severn, you may well need around 4ozs even in summer.........(that's IMHO). But in general, even on the bigger rivers such as these, 2ozs will suffice in a lot of places.
You don't say which river you are thinking of fishing, but contacting a regular on here may help !
Rod test curves can be deceptive as the action is far more important ! You will get a barrage of answers................To me no one is 'right or wrong' ! It's just down to personal preference ! If you have fished for larger fish (carp, pike, tench etc.) before, then you may well have an idea of the rod 'type' you prefer. This will obviously affect your choice........
I prefer a 'Through Action' (I-Power, Drennan Specialist etc.) And find 'Tippy' rods such a The Torrix, 'Feel Wrong' ! Others will favour these rods and the way they convey their 'Power'.
Like I say it's very personal !
I would ceratinly favour a 2lbstc rod for lobbing 5-6ozs feeders !
Finally, look on here and ask around (or make your own) for large feeders ! The Korum ons are great, but on a bad day some where like The Wye, it could cost you a small fortune !!!!!!!!
Hope this helps, but is no way definative, you will get many other opinions..........
Good luck and feel free to ask !
Regards Paul M.