Tbh, the drop off in marks from ranks should not affect you too much.
I came second for Phys.
Now top three got B6.
4th got a very low 70 (I think 72).
My assessment mark and third's assessment mark only dropped our final HSC mark by 1.
Reason why this happened is because our difference in ranks throughout the year was all proportionally correctly made by our teacher.
So by the time we got to HSC we were not highly affected.
In saying that if those below you do really well, then you could rob a few marks off them.
Even if say internally rank 2 and rank 3 had a 50% difference. Rank 4 and rank 3 virtually no difference. Ranks 1 and 2 virtually no difference. If rank 1 gets say 90 raw (and assuming this is highest), rank 2 80 raw, rank 3 70 raw, rank 4 60 raw, then the final assessment marks will be something like:
1: 90 obviously as unaffected
2: 88-89
3: 61
4: 60-61
as an example say.
So rank 2 actually got a lot of marks off rank 3 in the end. Note that all the marks add up. The cohort earns a specific amount of marks which is distributed according to their ranks and difference between ranks in a systematic manner, hence adding up perfectly to the same amount of marks originally obtained.
In saying all of this, dw, just try your best and you will be fine. Don't drop just because you are coming second and are worried of a huge drop in aligning. If you stay super close to first then you shouldn't go wrong.