The variant info for the model I'm working with is below.
I wanted to know if there were any users out there US or non-US that would be wanting or willing to test a 1520.3 ROM with me.
-You need to be able to understand and be capable of using Windows Phone Internals to unlock your phone
-Your device must be a 32GB model with Samsung eMMC
-This ROM is for the 1520.3 (RM-938) only, and was not tested for the 1520 (RM-939) or 1520.1 (RM-937). However, I own a 32GB RM-940 (1520.2) and this ROM does successfully flash to that device and work.
-Like any altering of any device outside of stock or OEM specifications, there is a chance for something to go wrong. Even though most errors or issues can be reversed or fixed you could potentially render your device useless or damage it in other ways. You would be willing to do this at your own risk.
-It would be best/ideal to do this with a spare device and not your main daily phone
I currently use T-mobile US so one of the customizations I did was to alter the NVI settings and provisioning files to use t-mobile US HD voice and LTE bands. I also removed some of the apps, and made a couple of other changes just for testing. I'm limited in what I can verify works for cellular tweaks and changes since I only use T-Mobile US.
If anyone is interested, let me know here and I'll post up a link to the image files. If not no worries. I'll link what I come up with either way at some point.
Model info: Lumia 1520.3 RM-938 Product code: 059V6X0 with 29.1GB Samsung eMMC
ROM info: Version 1703 Build 10.0.15063.1446
I've moved to another area of focus and so for now I ended troubleshooting and building this particular ROM further. However what I ended up with I have posted a link for as I said I would. The only real changes from what the original ROM was is I added my own NVI files under \Programs\CommonFiles\OEM\Public\Nokia\MultiVarian t\MCC-310\ and replaced the default variant NVI files with the same. I replaced the ADC files under \Programs\CommonFiles\ADC with that of the T-Mobile 640 LTE variant. I also removed some xap files that I personally found annoying or had no use for. That is about it.
Flash this at your own risk of course LINK