Scan documents longer than 14 inches with Brother scanner using SANE in Linux?

Question

I have a Brother MFC-L3750CDW. I would like to scan documents longer than 14 inches (long receipts) from the feeder. I have found many articles on Brother's website for how to do this with windows drivers, but not surprisingly they don't give Linux instructions. These all suggest to disable "auto deskew" and some other features to enable scanning beyond the normal maximum.

I have checked the options reported by my printer through SANE, and I don't see any option for this. I can set br_y, but it has a maximum of 355 mm (14 inches). Setting a value above this has no effect. I found this in a mailing list, but scanimage --ald doesn't seem to exist any longer. Here is the list of options reported by my scanner according to python-sane.

I found this related issue on Super User, but it's for a Fujitsu scanner. The solution given was to fold the receipt, but I don't want to do that. I want it to be as straight as possible because I am doing OCR.

Is there any way to enable this?

Here is the code I am using to scan the document:

import sane
sane.init()
dev = sane.open('airscan:e1:Brother MFC-L3750CDW series')
dev.source = 'ADF'
dev.br_y = 5000
print(dev.opt)
dev.start()
im = dev.snap()
im.save(filename)

Using scanimage from the command line, I am unable to force the scanner to use the feeder and not the flatbed.

scanimage --mode Color --device-name "airscan:e0:Brother MFC-L3750CDW series" --buffer-size="10MB" -y 355mm --resolution 150dpi --batch="test_crop_desk_%d" -l 43 --batch-start 0 --format=tiff

Which specifies both --device-name and --batch. It is still using the flatbed.