The problem with lowering a van and getting people's opinions on comfort is that it's all relative! If you have driven run of the mill cars most of the time, going to a van is a decrease in comfort. Then when you lower it your making things stiffer and even more harsh. If your used to sportier cars with stiffer rides the change to a van/lowered van isn't as significant.
This is my van. It's down about 160mm on Solow lows and 235/35/20 tyres. For me, the ride is great! Yes it is a bit crashy over rough terrain and it scrapes to hell over speed bumps, but on smoother roads and motorways it feels just like a sporty car would.
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How low you go, and what wheel/tyre combo you end up with is mainly down to what you can live with. But for me, low is the only way to go! Haha