Hello Ootoito, and welcome.
First, the strict message:
SEOW is not developed against UP. SEOW is only developed against IL-2 (which is now in the hands of Team Daidalos) and against HSFX. SEOW releases are intended to support IL-2 and HSFX. There are no plans for SEOW to support UP directly. Personally, I have never run or installed UP.
As I understand it, some past versions of UP included HSFX as a selectable option, but also added extra mods on top which can potentially conflict with pure HSFX. Therefore, in running a multiplayer SEOW campaign, there is the possibility of internal game conflicts between some players using UP+HSFX and others using pure HSFX. These conflicts may affect mission results and in-game combat performance in unexpected ways.
In any online war (SEOW or other), it is ALWAYS recommended for ALL players to use IDENTICAL game/mod versions. People who choose not to observe this rule do so at their own risk (and risk affecting other participants).
Now the practical message:
SEOW simply builds IL-2 coop files and analyzes IL-2 logfiles. As long as whatever game+mod combination you use recognizes whatever objects are used in the SEOW coops (planes/tanks/ships/buildings/etc) and writes out logfiles in standard form, the SEOW should work. SEOW does not care what game+mod combination is used to host the coop. You can add your custom "Fw190 -> Tiger Moth" mod (
) and run your SEOW mission if you want, SEOW will not care!
If, on the other hand, you wish to use a new object that SEOW doesn't recognize, e.g. a custom Mig-21 jet, then you can easily get SEOW to recognize it by adding it to the Object_Specifications and Object_Costs tables. You may also need to add a screenshot of it to the MP uniticons/IL-2 Object Images folder.
Cheers,
4Shades