at 16-17 lbs - you are over the best power to weight setup -in a 50 cc engine - any 50 I know of -

for really sparklin power to weight call it it thrust -whatever - with a 50 - you want to be closer to the 13-14 lb range.
Have I seen the DA 50 yes flown it - no - but watched after taching at 7200 on Mejzlic 22x8 - and definately the model needed more power. It was in the 16 lb range.
My new 50 ZDZNG is very comparable in performance and after doing a slew of 40 cc models - I can ffel confidant in saying that 14 lbs is about tops for really good 3D.
The engine will easily fly heavier models thru the patterns inc the Unlimited stuff.
My standard for a 3D model is one which will accelerate from a standing hover.
Your standard may vary---
for 16-17 lbs - a ZDZ60 - for 17-19 lbs the ZDZ80 single - I have that setup and it is excellent . The 3W 60-70 engines should also be great in this range-
no tuned stuff required.