It's been a dream in general use, returning good mpg, power and reliability....but it isn't such a great story offroad.

I've probably only used the van off the beaten track 3 times and on each occasion the clutch has heated up quickly and smelled for a while.
*I fitted a replacement Borg & Beck just before Busfest 2013 and while we completed the course (195/80R15MT tyres) the clutch didn't like it much.
*Then this year in August I drove the van over Pensard Beach, North Wales. As soon as any effort was required the clutch started smelling.
*Finally at Busfest 2014 we attempted the trail once more. This time we had a different interior setup (lighter) but 3 passengers and a full tank of fuel. We were running the 235/70R16AT tyres. The clutch heated up rapidly and by the time we reached the final obstacle (the hole) it really wasn't having it. Two failed attempts later the bellhousing breathers were chucking out smoke like the Devils nostrils and we have to be extracted by a Doka.

Even failures are worth remembering. A Syncro at this angle is photogenic and smoke is cool, right?

As embarrassing as some may have found being towed out, I was more annoyed with the van. It didn't ruin my weekend but I spent the rest of it thinking over the reasons.
I NEED it to be usable - otherwise I may as well have a 2WD. The fact that a Split bus (admittedly spiritedly driven, rocked and bounced) and a pretty stock Kombi T3 with skinny tyres managed to get around before me compounded my mood. I left the trail determined to fix this once and for all.
In retrospect, at the time of the conversion people recommended I fit a JX 215mm clutch. My past experience had me thinking this was on the small side (having owned lighter performance Golfs with 228mm clutches) but I went with accepted knowledge. Before the conversion I had a look at how a combination of a large rolling radius wheel/tyre combo, petrol syncro ratios and the AGG might work. Nobody could provide much by way of concrete information so in the end I bit the bullet and got on with it.
Since that I have gone through a Sachs HD and a Borg & Beck clutch. Both times were under load, on steep inclines and for short periods. I don't ride the clutch (in fact its a pet hate of mine) so this is downright annoying.
So where am I at?
Well the van is still drivable. I came home from Busfest at a steady 65mph with some slipping. I've also done the there and back to Back to Basics without issue but the clutch is now ready for replacement.
I'm running 235/70R16AT tyres, petrol ratios and the AGG (stock, 115bhp). Discussion with other Syncro owners at Busfest suggested that the AGG torque curve and peak delivery, longer gearing and larger rolling radius might be too much for a 215mm clutch. Perhaps not in normal operation but at peak torque under load and used in anger, possibly.
Now a gear ratio change and drivetrain swap isn't on the cards - I simply don't have the funds right now

With regards to the clutch I've read the 1.9/2.1 WBX petrols used a 228mm clutch (same theory as any well powered petrol?) and even Bays had the larger clutch. I've been told about VR6, TDI, 2.1 combination but no firm details. Is there a known combination of parts that would meet the task?
I'd welcome any input on the matter right now. My van is a lame duck until I get this sorted and I really want to go out with confidence and get some proper green laning and offroad time in it. Part of that has to be me learning the best way to drive the van of course but having confidence in the drivetrain is crucial.