SG and spare tire question

I'm putting a cone-style SG in the 8-3/4 for the Dart. My rear tire size is 27", but the largest tire I can fit in the spare tire well is only a little over 26". If I have a rear flat and have to limp along to get it fixed, will the slightly smaller tire cause issues with the SG? I'm looking at doing the temporary spare to save room in the trunk if that makes any difference. Top speed on a tire like that is 50MPH.