Looking for input on cabin plans

Hello!
We're just finalizing details before we break ground on a small light straw clay or chip slip cabin. Would  appreciate any advice, tips, or constructive criticism  of our ideas.

Location is a Southern Gulf Island, BC (PNW) so rain is a factor. 16×20 cabin. Concrete slab foundation and 18inch stem wall. I know 12 inch wall width is standard but we are considering 10 inches to save on floorspace and drying time, will this be an issue? We have a relatively mild climate. Double stud walls (gf doesn't want to go the Larson truss route as she's worried about  splitting the thin wood). Metal roof for rainwater collection. Planning on an earthen floor, woodstove for heat. Clay plaster interior and lime exterior, hoping that will help with the water. 2 foot overhangs.  Still  deciding  between chip slip and straw, we have access to free chip but it's quite large chunks, we could potentially send it through  another  chipper to make it smaller. Will do some tests first before we make that call.

Future plans/amendments that we are taking into consideration are; a covered porch, covered cob oven/outdoor kitchen area, and either a masonry heater or RMH.

If there's anything I missed or any glaring issues please  let me know! Hoping to start in spring.

I don't see anything glaring, but as far as input goes, anything specific you're looking for? Providing some more details/plans/sketches might help...

2' roof overhangs sounds pretty good, depending on wall height and exposure. You might want more on a windy side or if the wall is taller than one story. A 2' overhang on my east side protects a three story wall pretty well, as I rarely get wind/rain from that direction. On the west/south sides, the lower part of one story walls gets wet.

If you don't have examples nearby to go by, I might make a mockup of toolshed scale with walls and overhangs the same size as you are thinking of, and see how they behave in the weather for a while.

Straw has lots of little hollow spaces, so would most likely be a distinctly better insulator than wood chips in a mix.

You may want to consider a full wrap around porch.  That way water should never touch your walls.  

The porch to the south could be walled in with glass to make a greenhouse and add supplemental winter heating.  If you design the overhang right it can collect winter sun but provide shade in the summer.

Think through every joint on the building.  I am building a log cabin and last minute I decided to use joist hangers for the floor joists instead of pocketing them into the walls.  Now that it is fully built I just realized pocketing them into the walls was what was keeping the tops of the walls from bowing out so now I need to go back with cables and steel plates to prevent the walls from pushing out with time.  

I also made a mistake with the birds mouth on the rafters so I have to go back in and cut them all off and bolt in a couple 30 foot 4x8's to give the rafters full support.

Since I am building it all myself with scrounged material those aren't huge problems but with a bit more forethought I could have avoided them.

If you are building it yours self have a plan for every stage of the building, as well as a back up plan and a double back up plan.

As an example. You plan to frame it with wood and fill it with a slip mix?  What if the slip mix wont stay or shrinks as it dries?  

Re filling between framing with a slip mix: You want a key at each side of the cavity being filled, whether it is a 1x2 tacked onto the framing or a groove cut in it. This will positively keep the infill from shifting, and reduce air infiltration through the joint between materials.