Let's look at the numbers of the other Cromwell nerf:
Weapon | Accuracy (N/M/F) |
AT gun | 0.06/0.05/0.04 |
Ost Panzerschreck | 0.069/0.052/0.028 |
OKW Panzerschreck | 0.05/0.0375/0.025 |
Weapon | Size 18 | Size 23 |
AT gun hit chance (N/M/F) | 100%/90%/72% | 100%/100%/92% |
Expected AT gun shots to kill (N/M/F) | 4/4.44/5.56 | 4/4/4.35 |
Ost Panzerschreck hit chance (N/M/F) | 100%/93.6%/50.04% | 100%/100%/64.4% |
Expected Ost Panzerschreck shots to kill (N/M/F) | 6/6.41/11.90 | 6/6/9.32 |
OKW Panzerschreck hit chance (N/M/F) | 90%/67.5%/45% | 100%/86.25%/57.5% |
Expected OKW Panzerschreck shots to kill (N/M/F) | 6.67/8.89/13.33 | 6/6.96/10.43 |
The effect of the target size change is mostly in the Cromwell's ability to kite and make hit-and-run attacks. It does seem to be a little much given the sizes of comparable tanks (20-22) and that the Centaur is also size 18.
Looking at the stats, I think the OKW Panzerschreck might need an accuracy buff now it's on Sturmpioneers.