I am still looking for a workaround to resizing in Qimage Studio
No workaround is required - it does it, it's one of the main features.
Place the image in the queue, right click on the page preview and choose Convert.
Click the dot Add to/Replace existing filters,
In the dialogue that pops up, change the resolution, near the bottom of the dialogue.
Click done, make sure the file type and colour space data is set as you want and then OK.#
That's all there is to it
Can I fool my PC and Qimage that I have a larger printer
No! The driver is the driver for your printer!
If it had banner mode you'd be ok. but not so for the 3800
Terry