The RIGR is very hard to come by, in case anyone around here has some volumes I'll throw this out here:
In researching James Smith, I found that Guild (linked at the profile) provides a lot of information, including noting that the executor of James's estate, his son Nathaniel, conveyed land in 1774. But Guild says he found no record of the will. Today, I came across a statement in "Mayflower Families" v.23 part 3 that Beaman abstracted this will in RIGR and mentions children not found in other sources, like Jerusha Smith who married John Bullock.
The entry is supposed to be in RIGR 1:4:208. If someone has access, I'd give a big gold star and a lot of appreciation for a lookup.