Harborside Stuck in the Arch

Between helping customers in the store, taking inventories, placing orders for restock, straightening up the shelves, checking and packing up online orders, updating the website, and replying to emails, I try to fit in an hour or two of work each day on customer's houses in the store.  Since I only get to work for an hour or two, work is slow.  But I felt I made huge steps yesterday in cutting out the arch on the Harborside!  My I-drill (I love my I-drill!) worked great and I had the arch cut out within an hour - I was ahead of schedule!  Maybe I would also mix up the ceiling paint and start painting ceilings!  But first I should test fit the archway trim . . . .

Customer has a Lawbre arch for the doorway from the kitchen to the addition conservatory room.  I love this arch (not that my opinion matters for much, but there it is)!  I have it as well for my Victorian Fantasy dollhouse but have not yet installed it because my Victorian Fantasy dollhouse has a double wide opening so side walls must be cut out and the top opening of the doorway must be filled in before the arch will fit (i.e. lots of other work must be completed first so it hasn't gotten done yet).

On the Harborside Mansion though, it fit beautifully once I cut out a little bit off of each side:

Arch cut into main housebody.

Arch cut into addition wall.

Arch trim looks fantastic in the space!  Oh, wait, I have to put the addition onto the side of the house too and then put on the archway trim!  Oops.

The disappointment came after I had cut the arches and discovered that the Lawbre arch fits over a 3/8" thick wall.  But in this dollhouse it has to fit over the exterior wall of the main house body (3/8" thick) PLUS the addition liner wall of the conservatory (1/8" thick).

When adding an addition to a Real Good Toys dollhouse they provide a liner for the side that butts up against the main house.  If the dollhouse has milled siding, such as the Harborside Mansion, it covers the milling so that your interior addition walls are smooth for decor.  But it creates a thicker wall.  Now the arch does not fit.

Channel inside the arch trim will not fit over the two walls together.

Even when I press them together, the two walls are just 1/8" too thick for the arch trim.

Solutions?
Well, there's the first possibility: a labor intensive and risky solution of routing out the wall(s) or cutting out the liner in the exact shape of the trim so that the arch trim fits into a snug groove.

Lots of detailing to route out around precisely.

But there is so much detailed trim on the arch trim that cutting out for it will take time, a steady hand, more time, and lots of potential for mistakes that will have to be filled in with Spackle or wood fill.  It will also look poorly when the trim is not snugly in place (as cutting out will be done by hand so some parts will be jagged and uneven).  But it's possible.

Second possibility is to remove the addition liner wall (or cut most of it away so that only thin strips support the ceiling piece) and fill in the siding with Spackle so the milled nature of it is covered and painted smooth.  The wall is only 3/8" thick so the trim fits again:

With paper and a spare piece of crown molding I created the look I am trying to describe.  You have to imagine the rest of the conservatory is there (ceiling, floor, front wall, and other side wall).

Without the addition on it, the house will always look like this.

So the decor for the one wall of the conservatory will always be attached to the main house body.  Looks odd without the conservatory up against it, but how often will the conservatory not be up against the house?  During transportation and/or moving?  That would be okay.

However, what is not okay is that by removing the addition's liner wall, the corner of the ceiling has no support where it meets the back open end of the dollhouse.  What would the ceiling rest upon to keep it from sagging over time?  (Now, some other miniaturists have assured me that the ceiling would not sag - it is structurally sound due to cantilevering or something like that, but I am a worrier and cannot help feel that it would sag over the decades and my customer has too much invested in this to have a saggy dollhouse!).  My only solution to that potential future issue is to either 1. permanently attach the addition to the main house, nailing thru the walls into the conservatory ceiling/roof or 2. attach crown molding to the main house body so that the roof of the conservatory has a solid piece to rest upon (since we removed the liner it previously rested upon):

Ceiling/Roof piece would receive extra support from the crown molding if it needed it.

So today's hour or two will be spent debating pro's/con's of these two solutions while still drinking lots of coffee in hopes that a third option materializes in my mind!

Any suggestions, Mini Friends?  I would appreciate any thoughts!