I've been riding the takuma 1600 and 1300 foils for a while now for winging / downwind. As far as shims go, definitely use them, thickest part to the back

. The 1.5 as a minimum and possibly both (from my measurements the stock shims change the tail incidence less than stated, so I made my own). I ended up settling on a tail incidence of -2' to the main foil. This works for both the 1600 and 1300.
For something different, a couple of days ago I got around to trying the 270 tail (small one) with the 1600 foil. I expected it to feel quite loose and pitchy. Instead I was blown away by how good it went. It definitely is a little bit more pitch sensitive. This is quickly adapted to. It still feels locked in and pumps well. The big difference is it has just opened up the top end more, giving better acceleration and speed but it hasn't affected low speed performance. If anything it has improved, which still doesn't make sense in my head. So this leads me to think do we need tails at all?