I've got 105mm clearance under my Plus 8 sump with 205/55 R16 tyres.

My 1993 Plus 8 on 15" 70 section tyres had 100mm clearance, so ground clearance has never been a problem for me unlike the 4/4 Sport which got the crossmember clouted several times.

2009 4/4 Sport Henrietta
1999 Indigo Blue +8
2009 4/4 Sport Green prev
1993 Con Green +8 prev