Which scene are you trying this out on? Which looks?
It'll be easier for us to help if we know what you're dealing with.
Swapping characters into any scene works fine for me. There's the old method and new method.
I never had scaling issues before, but also I'm not too clear on your situation.
I use LOAD LOOK for older VAM versions of characters and APPEARANCE PRESET for newer versions of characters.
View attachment 1818913
View attachment 1818914
I'm using Looks of video game girls mostly, from pseudo life-like generic / typical body shapes (Life is Strange, Lara Croft, Ada Wong, Jill Valentine from the recent games, and similar 'normal human shapes' characters) that don't have many unique body proportions... to hyper stylized characters like Genshin Impact, Overwatch or Valorant, etc.
All characters I download have their scale to 1.000 all the time by default (all the girls anyway, can be different for some males though). However, it doesn't change the 'fact' that some specific characters are small anyway. An example would be, say... Tracer from Overwatch, she's small. She has a thin body frame, her height is not the 'typical' 1.000 female height you'd expect for the majority of scenes. And most males next to her are like Titans. So already when the scene starts, the height differences (regardless of scaling set to 1.000 for both of them) everything misses. She's too small to reach the dick when she's supposed to grab it (or arms are too short, etc), when she's on her knees for a blowjob, she's sucking air.
And to "compensate" for that, I have to reduce the male's scale to oblivion to even just make sure that the body parts connect (hand connects to dick for a handjob, etc), but then if I do that, the male's dick becomes much smaller. However, even if I go in Male Morphs and increase the dick's size or length, it doesn't help. Then I use a Plugin like Divining Rod, let the default values and the dick just constantly tries to reach the mouth (in case of a blowjob) but instead just robs itself against her face sides and never 'gets in'. So, to make the dick go in, I then have to manually go to the male's Root Node, grab one of the directional arrows and move the guy back enough so the dick's "searching" from the Plugin can finally find the entry point of the mouth and finally make it work. But as soon as the female's head moves or rotates during the blowjob animation the dick sometimes just decide to suddenly pull out, just... like that, it's out. So I increase the length or girth further to make sure it stays in... nope... doesn't work; if I do that, the physics of the dick starts twitching and contorting to impossible angles and eventually I just give up.
So far I haven't found more than maybe 2 or 3 sex acts scenes out of something incredible I've download worth many GBs of data from the Hub. Maybe a total of basically all the Free scenes I could find, + two Patreons I found that I subscribed to to get even more. I tested a good 50+ scenes so far, and I kid you not, only 2 or 3 of them for some reason have enough of leeway where I can replace the default girl with something like a stylized one AND replace the male with a Futa or a Demon or something crazy and it still mostly all work. But the vast majority of scenes I'm doing my character / Appearance replacements with just don't work anymore as soon as I change anything on any one of the characters.
I do mean sex acts here. Because obviously anything that's softcore / dancing / solo characters is fine, sure. That does work. But character connections / body interactions? Forget it, it's a nightmare so far.
I'm using Divining Rod for all the scenes where it's not there for a start (but the scenes that don't use it DON'T have any issues with the default characters, everything works; the author didn't need the Plugin to make the scene work), and I'm also using stuff like auto Bulging stuff (when it does work and the dick gets in... otherwise it's useless). But generally speaking I simply try to use a pre-made scene, go to Appearance, upload my Look and cross my fingers something works. It very rarely does.
