OpenEXR and R13

I am changing my pipeline to accomodate OpenEXR for the following advantages:

• All channels in one file (no messy directories)
• 32-bit 
• lossy compressions available 

These are the downsides

• You cannot re-render just one channel (ie a mask), but from experience I have rarely only rendered one channel, plus it looks like C4D would have to render to whole image anyway, so not a lot is gained. For special cases, such as masks I will generate subdirectories and they are highly compressed anyway.
• No 16-bit support in R13 (maybe, they'll bring it back) - so the only option is to go with 24bit lossy, which according to forums will just truncate 32->24 bits and rezip the file. For my purposes this is more than enough, as I don't layer a lot of stuff.
• ExtracToR in After Effects is rather slow, but this seems to be related to the file transfer.

For my test frame, I was faced with those sizes (I didn't measure multichannel here)

• All compressions RLE, ZIP, ZIP16, lossy PIZ wavelet, etc around 20-24 MB
• The 24B format comes in around 12 MB (ie half)
• A 16-bit PSD file comes in at around 12.4 MB - so 24BLossy is the way to go.
• 8-bit DPX is 6.2MB

So with 24 bit lossy format I gain more than enough control.