Ummm, depending on how you look at it, there either isn't a problem - or the problem isn't going to be solved by putting the shield in the mil-slot anyway.
You could go for something like this:-
3A Fuel Scoop.
2G Vehicle Bay.
1A Shield Generator.
1C Disco' scanner.
Presumably, you're going to want to take a DSS with you as well.
If that's the case, ditch the shield.
The real problem is, the 2C fuel-tank doesn't leave you much room for error so ideally you might want to fit an internal tank too.
And then there's the likelihood you'll want an AFMU too.
Which means you still have to pick other stuff to get rid of as well.
Personally, when I went to Sag A in a Sidey, I fitted it with a 2A scoop, 2A tank, 1A AFMA and an ADS.
No shield, no SRV and no DSS.