Although it may be feasible to get a grip of the twin in only 6 hrs, it does sound a bit on the low side. It really depends on your previous experience.
I'm not sure what the JARs say about this but what I've heard looking into it is that without an IR and/or CPL you need 15 hrs training. If thats regs or reqs I'm not 100% sure of.
I'm going to do mine in a Seneca soon and with a CPL and IR my instructor still says I should look at about 10hrs, even though he says I can do it in 5-6 hrs according to JAR.
100hrs P1 doesn't say alot about your experience level.
What types have you flown, CS-prop, retract, high performance etc. ? And do you hold IMC or IR ?