The water in the spines actually helps transfer heat better. Much research has been done on the subject of spiny pipe versus tubes and fins. Main ideas: spiny pipe costs the least to make, has slightly lower efficiency than tube and fin, and is harder to clean. Easy to flush, though. Dehumidification factor is the same. Parallel micro-channel and fin designs beat them both by a substantial margin, but cleaning and flushing them is much more difficult. Automakers have pretty much all switched to micro-channel condenser coils, so a contamination event pretty much necessitates a new condenser coil.
At 66PSIG, you are pretty close to freezing your coil. I try to keep mine above 60 during trials, as frozen things happen around 55. That's with propane. If you are running propylene, this happens around 70. Blend is somewhere in between.
Preliminary numbers look pretty darn good to me.
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