Trailer Help

[woot]

Apologies in advance for this not being strictly RIB related but I will try and make a tenuous link. My neighbour has recently bought a small fishing boat which I have launched with him a few times. Launching is fine but recovery is difficult even on easy slips. The boat always seems to roll off to one side of the keel rollers at the stern end. My 5m Humber ( RIB link ) had a Bramber rollercoaster type trailer which was an absolute doddle to recover onto even if the boat was at an angle it would straighten itself out. He has tried adjusting the bunk heights but this doesn't seem to help.
Would changing the side bunks to pivoting rollers help? How else without major reworking can he keep the boat centred as he winches on?
I have attached some photos which show the offending keel roller and bunks.

[Nos4r2]

If what I'm seeing is right I'm not surprised he's having trouble-the keel rollers aren't V-rollers are they? They should all be and the photos look like they aren't.

[BogMonster]

I have been looking at lots of pictures of commercial trailer designs with a view to modifying my home brew one (built by previous owner) and they mostly seem to use the pivoting side rollers to locate the boat as it comes on to the trailer, with the keel rollers placed further forwards. Not sure what I am going to do yet but I had the same problem with mine the other day, ended up with the boat a bit cock eyed on the trailer. Hit a few potholes on the way home and it was in the middle by the time I got home

I nearly got the Land Rover bogged with the boat and trailer on the back too, but that is another story...