I hold quite a few Dash and I regularly mix them with DS (3 rounds usually). However, any attempt to send large Dash amounts (either through Normal or Darksend or IX) will fail with a 'transaction too large' error. This can be as small as 50 Dash. The interesting thing is that within Coin Control I was selecting all non-masternode inputs so it should have selected the right ones, however it still refused to go. What I did was to slowly transfer normally into one Dash address and consolidate it all in one address and only then was I able to send 1000 Dash out. Is this because each Darksend denomination is only 0.1 and too many inputs are required? Sounds like something is buggy though.