Craig Criddle posted the following on RfM:

Here’s a hypothetical timeline for the “translation” that is consistent with the Spalding-Rigdon Theory:

1809-1814 – Spalding wrote Manuscript Found, a precursor to the BoM that contained the historical parts.

around 1814 – Rigdon copied Manuscript Found

1823 -1827 – Rigdon added Disciples of Christ and Arminian Theology to Manuscript Found

around 1826 – Rigdon and Smith agreed upon a plan to create a new American scripture. Smith would act as the Seer and would reveal the new scripture to the world.

September 1827 – Rigdon gave his modifed version of Manuscript Found to Smith

April 12-Jun 14, 1828 – Smith “translated” the first 116 pages. Harris was the duped scribe. Translation rate was about 2 pages per day.

June 1828 – Harris lost the first 116 pages

July-Sept 1828 – Rigdon revised Mosiah through Mormon 7, adding some more Disciples of Christ doctrines.

Sept 22, 1828 – Rigdon gave Smith the revised version of Mosiah through Mormon

7. Oct 2, 1828 – Mar 15, 1829 – Smith translated the revised version slowly (0.5 page per day) with Emma as his duped scribe. They only made it through Mosiah.

Oct-Nov, 1828 – Rigdon wrote 1 Nephi and part of 2 Nephi, adding more Disciples of Christ doctrines.

Dec, 1828 – Rigdon gave 1 Nephi and part of 2 Nephi to Smith.

Jan-Mar, 1829 – Rigdon wrote Mormon 8-10, added Ether, finished 2 Nephi and added more Disciples of Christ doctrines.

April 6, 1829 – June 6, 1829 – Oliver Cowdery assisted translation of Alma, Helaman, 3 Nephi, 4 Nephi, Mormon 1-7. Translation was rapid (6 pages per day). Method of translation = copying (so it’s fast).

May 1829 – Rigdon finished 2 Nephi, Jacob, Moroni, Enos, Jarom, Omni, Words of Mormon and gave them to Smith after adding more Disciples of Christ doctrines and details needed for Church organization.

June, 1829 – Translation proceeded rapidly through Words of Mormon. Method of translation = copying, with some duping of the Whitmers. Cowdery probably helped with the editing. Time to “translate” = 5.5 months of dictating to a dupe + 3 months of copying = 8.5 months