That's what I've been running for months now. ie screenless, vaneless MAF 3" Housing with 3.5" sensor.
If you look back thur the last several months I've well documented what I've done. In MAF mods
In short:
75mm = about 3 inches.
If you cut the vane and supports out of the small housing you have about the same cross sectional area as the stock 3.5 housing. Then with a little trimming you can run a 3.5 sensor in the 3" housing. The sensors are identical other then the electrical guts, and locating tabs.
BUTTTTTTTTTTTTTTTT,
You have to totally recalibrate the MAF Tables and Scalers to get the calibration right. I have alot of quality time with the WB and making chips to get things right, but it can make for a neat setup.
If your worried about flow, you want to change to a blow thru set up. That way the turbo is blowing pressurized air thru the MAF rather then having to try and suck the air thru it. A blow thru MAF with screen and vane can run just fine with the normal Extender chip, well it did in mine anyway.
If your thinking about the Vanless Screen blow thru,
figure on 100 or so chips. Recalibrating a MAF is some serious effort.