Hippy has forgotten more about distance TTs than I ever intend to learn, listen to him, particularly about position. It might help, though, that if you can ride 65 miles at appx 15mph with your mates and your target is 20mph for the 100, you'll only be on the bike for a bit over half an hour longer. A fair bit of the speed increase will come from aeros and a bit more from concentration and not sitting up to wait for others. You won't be last!
Hippy has forgotten more about distance TTs than I ever intend to learn, listen to him, particularly about position. It might help, though, that if you can ride 65 miles at appx 15mph with your mates and your target is 20mph for the 100, you'll only be on the bike for a bit over half an hour longer. A fair bit of the speed increase will come from aeros and a bit more from concentration and not sitting up to wait for others. You won't be last!