E90 touring Space saver ? and non RFT pressures

[Farmer]

Like many folk I've just ditches run flats , suddenly after discovering metal poking out of the inside edges of my 2/3rds worn rear tyres (but that's another story I'm currently in dispute over what constitutes "aproved used") Now have 17" eagle asymetrics and was wondering what the consensus is on tyre pressures for non runflats compared to OEM . also wondered if anybody has successfully managed to stuff a spare wheel of some description under the boot floor of a touring . There is currently a shallow tray and a deep square box . Quite happy to use a space saver, not ideal but better than tyre weld and compressor used now.

thanks

[Farmer]

any sugestions?