| Porsche | Model Year | Closest distance between forward towers - (M1) | Distance from uppermost windshield to forwardmost tower foot - (M2) | Closest distance between rear towers - (M3) | Crossbar spread distance center to center - (M4) |
| 924 | 79/82 | Q4 - 38 3/4" | 6" | Q4 - 38 1/2" | 25" |
| 928 | 79/93 | Q30 - 39" | 3" | Q4 - 39" | 20" |
| 944 | 83/91 | Q4 - 38 7/8" | 5" | Q4 - 38 3/8" | 26" |
| 968 | 93/94 | Q4 - 38 3/4" | 6" | Q4 - 38 3/4" | 24" |
