I think Sterling products are top rate, but I also think that George is taking this experiment to the limit. It will probably apply more to caravaners as the 7 pin trailer couplings are always a issue for making good contact joins. So a lot of his issues would have been at the trailer coupling pin.
I use a 140 amp split charge relay with 70 amp cabling. Previously I used 20 amp cabling using a 10 amp split charge relay. Using the same gauge I found very little increase in charging rate between both systems. It certainly didn't solve my recharging issues. I still have to 'bench' charge my leisure battery as we to do very little mileage.
I had thought of buying one of these for the new van and trying it, but Numax once told me that charging a leisure battery at 10% of its capacity (110 amp leisure = 11 amps) is the ideal. However, George is charging his caravans battery at 28 amps. (I couldn't make out what battery George is using. Someone asked but there was no response. I'm sure he did say it was a 110amp but I don't recall him saying if it was a starter or leisure battery. I did look on the internet for the battery make, but still not exactly sure. The one listed that I saw was a dual purpose battery - starter and leisure.)
Thank you Spruce for your comments.
I had not heard of the 10% of capacity charging rate before.
Every day's a school day! 
I really think that I don't do enough mileage in a day to make a normal split charge system work effectively for me.
And in hindsight this Battery to Battery Charging with the high charge rate probably won't be a long term solution then if it could potentially decrease the life of the Battery.
So it's given me some perspective and I will probably now swing towards charging the leisure battery up with a 240 volt smart charger in the van and get an outside socket fitted.
Unfortunately, this is the unknown quantity.
Since this discussion with Numax a number of years ago now, dual batteries are becoming more popular in the leisure industry. So does this mean that because they will support short outward bursts of high amps starting an engine that they will also tollerate a higher charging rate? I guess we need to ask them the question.
We all know that alternators make very poor battery chargers, but they don't need to be any better. What they are very good at is keeping all the vehicles electrics (rear screen demister, heater fan, heated seats, radio and headlights) supplied with enough power on idle. So all it needs to do is supply enough charge back into the battery to return what the starter took out starting the vehicle.
In our speak, a couple of seconds starting a 2 liter diesel engine will take about as much current as one of our water pumps does in an hour. So maybe with fancy electronics we could charge them faster.
But I haven't heard Dazmond saying that sometimes he puts his battery on charge only for the charger to switch off immediately. This would seem to indicate to me that his battery to battery charger isn't the total solution for our industry if we travel short distances.
A decent size solar panel on the roof with a quality MPPT controller will probably get you by from spring through to autumn, so that could well at least save you 8 months of lugging a battery about.