Rollei Ortho and Rollei Blackbird, both pushed quite a bit: _how_ long to cook?! :O

[PilafDM]

Good day, everyone!

I was getting a little crazy and wound up shooting these two rolls:

• Rollei Ortho ISO25 (shot at ISO75), and
• Rollei Blackbird ISO100 (shot at ISO 450).

I'm currently only able to access a darkroom which stocks some Arista academic-grade developer, which I _think_ behaves like D-76.

People talk about pushing the Ortho as far as 100 in some developers (to which I've no access). For D-76 at 25, 6 minutes at 20C appears to be recommended on the Massive Dev Chart.
The Blackbird, though -- I've heard nothing except pulling, not pushing. Developing it at 100 in D-76 is listed at 10 minutes at 20C on the Massive Dev Chart.

Now, the Massive Dev Chart also recommends multiplying development times by 4.5 (!!) if using a plain ol' developer when pushing about three stops like I am.
Since I can't find any information to the contrary, am I to assume:

• Ortho: 6 minutes * 4.5 = 27 minutes (?!)
• Blackbird: 10 minutes * 4.5 = 45 minutes (?!)

Those times sound awfully long. I suppose my thoughts are:

• Has anyone ever similarly pushed either of these films and have some times for me?
• Should I go ahead and use the recommended push multipliers and develop that long?
• Is it better to risk over-processing than under-processing? (Can film be cooked too long?)
• Should I attempt maybe a different water temp or agitation regimen?

Any help appreciated!

 

[ann]

Rule of thumb 15-25% per stop.

Frankly, i never use the box speeds.

so you are about 1.3 stops for the ortho and 2.5 for the blackbird.

Don't know where you getting 3 stops.

 

[PilafDM]

Rule of thumb 15-25% per stop.

Frankly, i never use the box speeds.

so you are about 1.3 stops for the ortho and 2.5 for the blackbird.

Don't know where you getting 3 stops.

I love the "I never use the box speeds" ethos. Bravo.
As far as my faulty math, I wrote the post in a hurry at work and didn't think about it. You're right, I was way off.

 

[ann]

Well, i have tested for my equipment and that's why