I think I have ALL my "objects" kill again by using "Set xyz = Nothing"
Aside from whether or not an object is persistent when the module is still in effect, that will only have an impact on machine memory. It will have no effect on the size of your db. As for 25 vs 4 Mb, that's not serious unless your pc resources are quite small. There are many things that can cause this (speaking of when much of it is recoverable, thus has nothing to do with how storing attachments causes severe bloat). For your peace of mind, the occasional compact/repair should suffice, or you can write code to effect a c/r if the file size exceeds some arbitrary amount you specify. I wouldn't turn of c/r automatically, which is an option setting.
BTW, you didn't say which half was a "problem".
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.