The OFA gives you guidelines to have one or more versions.
That's why you have "product/806" and "product/816"
So you could have.
/u01/app/oracle/product/806
/816
And they can be mounted in different logical volumes ..say.. 1.5Gb each one (could be 1G)
Don't forget to set right the oratab and execute oraenv so you don't have to set ORACLE_HOME everytime you enter; or you can create 2 users beside oracle, i.e. oracle80 and oracle8i