Thanks for posting back on this.
Was going to post a thread on this until I saw yours,
and previous one being from 2015 Feb.
went looking for videos "Duel boot TrueOS", and found zilch.
I am trying to Duel boot a 3Ghz, 8GB, Thinkpad x260 with 260Gb,
100GB for win7, & 250 for TrueOS.
My first few goes did not work. Being a long term Open-Suse user(now using Mint allot), I thought
TrueOS had a boot menu installer as an option, and was surprised to discover not.
I got as far as installing most of TrueOS, but could not finish out install with
clean exit, so that any boot loader, pointed at partition could load, TrueOS(or Win7).
Bit disappointed, as I want to use TrueOS for 90% of the time.
I have downloaded the recommended rEFInd, and reading up.