If he is getting it stuck to bum, I would definitely recommend Oxbow then. Although we have "instances" which are very rare now (mainly when he is due a dental), Homer has huge golden poops.
They are smaller pellets than SS (similar to Excel I think)
If you would like me to send you a handful to try PM me your address and when I get my delivery next week I can send you some (we are running short at mo!)
I also give pro-fibre but they are more of a "treat" instead of fenugreek crunchies
To be honest, neither them or fibreplex seemed to have helped in the past.
You could also try feeding hawthorn leaves, I have definately found then have helped.