Additional SSD HDD (keeping Optical Drive)

I've replaced my existing hard drive (250GB) with a 1TB drive and now I've got the ifixit bug!

I realise it's easy to replace the optical drive with an SSD but what if I want to keep the optical drive intact and just slip in either a 1.8 or 2.5 inch SSD?

Furthermore, I realise that the more recent Macs have the option for an SSD and they have unused SATA cables on the inside but mine didn't have the option and has no spare SATA connections to use.

Questions:

1. Can anyone suggest if it's possible to use some kind of double adapter on the existing HDD's SATA cables (power and data) and for the Mac to recognise it as a second drive?

2. Any suggestions for where to find SATA power and data double adapters?

3. Can anyone suggest where there may be room to squeeze either a 1.8 or 2.5 form factor SSD? (Since it emits very little heat, I really don't mind where it goes)

Thanks in advance