As I discovered in UPBGE 0.3+, setting up a linked overlay HUD is extremely painful now. It was once a very easy process, put another scene on top, worked flawlessly. Come 0.3+, they tore out this perfect system, and now, object physics get broken when we add a linked overlay collection from another file, weird behaviour with the collection duplicating itself occurs, setting up menus is next to impossible now and this weirdness never existed back 0.2.5 and prior. Why tear out a perfectly good, tested system? This makes me frustrated, and is more game-breaking than fixing.
UPDATE: I followed this video here, and tinkered around with my own HUD, and discovered that when you link the overlay HUD, you must uncheck Instance Collections, or else your collection will have a duplicate in the level that uses up performance and is undesirable in the case of HUDs and UIs.
Problem with HUDs, are that detailed HUDs/GUIs will eat up performance. Can anyone show me how to avoid this when linking a HUD and unchecking Instance Collections?