The LR87 had a diameter of 1.53m and 1.14m (depending on the variant) but the VAB shows them all as 3m.  Aerobee on a 1m diameter probe core  LR87 on a 1m diameter probe core  Vessel with 1.7m diameter boosters (6.5m total length)  Vessel with 1.7m diameter boosters + LR87 engines (7.8m total length) 