Hi Josey
Thanks for your PM, which I will respond to shortly ... and also will endeavour to assist on the thread, with some of the newer queries you have.
Still somewhat hampered by having the NZBDM site not operational (hopefully it will be back up and running by tomorrow).
"No SMART's on 1851 passenger list". Mmm ... I do wonder if the STUART people (William and John) are in fact the SMART brothers

I can see how bad writing might have seen the name transcribed as "Stuart". (More letters of course in "Stuart" but both names end in "...ART". ) ??
And you do have verification (from William SMART's obit) that he arrived per the "Isabella Hercus" with his brother John.
I tend to think that the groups listed in the Cabin and Forecabin, were all persons who paid their own fares to the Colony. The "Isabella Hercus" was amongst the first six ships which brought the earliest emigrants to the province of Canterbury (a new venture for the Canterbury Association). To help offset the cost to the provincial government, passengers who were prepared to pay full fares, also sailed on these ships. [ I can see that Archives New Zealand in Christchurch, hold quite a lot of files in relation to this 1851 voyage ... but it may well only contain info on "the emigrants" (i.e. those persons whose fares were paid in full or part by the provincial government.) Anyway I'll get back to you about this once I've had a closer look at the file references. ]
The "Bill" referred to in Richard's diary, might of course be William SMART ??
Have a lot more info to add here - it's getting late - so will post further tomorrow.
~ Lu