I think the discussion is mixing several different issues and treating an installation order as a proven compatibility solution when it isn't.
Regarding Doodmane444's June 23 report: the tested order was K1CP → Sleheron → BOSSR, and some placeables disappeared in BOSSR modules. However, the suggested alternative still placed BOSSR last. It mainly changed the order between Sleheyron and K1CP, so it doesn't establish that this arrangement actually solves the underlying BOSSR placeable issue. As JCarter426 pointed out, if BOSSR is exhausting the available placeable rows in placeables.2da, changing the installation order cannot magically increase that limit.
There is also the reverse side of the problem. OnJuly 2–3, Doodmane reported that BOSSR could replace leftover, unused Czerka sign placeables in Sleheyron's sle_m30aa.mod with its own stasis NPC. He traced this to obsolete placeable entries left in that module after the signs had been built into the model instead. This is a concrete example of BOSSR affecting Sleheyron, rather than the other way around. It is also a specific module/resource conflict, not proof that one universal installation order fixes everything.
So I think we should distinguish between:
1) conflicts caused by overlapping or reused placeable references;
2) the actual placeable row limit;
3) installer overwrites and changes to shared resources.
These are not necessarily the same problem, and they cannot all be solved by simply moving one mod to the end of the installation order.
For players who want to enjoy both expansions without potentially ruining an existing modded installation, I would suggest keeping separate game folders:
1) Keep the existing installation for BOSSR and its associated setup.
2)Make a copy for a Sleheyron-focused playthrough, installing Sleheyron and its relevant compatibility patches there.
3) Start from a save made before the Dantooine Jedi Council mission, or use the save provided with Sleheyron, which starts at the intended point in the story.
This doesn't magically make the two mods compatible within one installation, but it provides a practical way to preserve both playthroughs without repeatedly rebuilding the same game or risking the original setup.
The current Sleheyron 3.5 instructions do provide a specific combined installation order and compatibility patches. However, I would still like to see reports from people who have actually completed substantial portions of BOTH expansions in the same installation.
Ideally, such reports should specify the exact mod versions, installation order, and which parts of both campaigns were actually played. Loading a save or reaching a particular planet is not the same as demonstrating that the entire setup is compatible.
I think that would be much more useful than continuing to assume that one installation order automatically protects one mod from the other.