Thanks. Yes, I added ~12 stops. The exposures were, IIRC, something like f/8 and 2 sec in sunny 16 light. Handheld! (Okay, braced, but handheld nevertheless

) Mind you, I rate the Rollei at 400. Typical for me, with this film, is to make up about ~9 stops of compensation by going to ~ 2 sec or 4 sec exposures, and then I just open up the lens from f/16 to do the rest. EV+11 also works quite well.
This one was also done with similar compensation and also the 87 filter....
http://keithwilliamsphoto.net/Photography with Invisible Light/Mares and Foals.html
The main thing with IR is that it's all about the light you have... the exposure comp factors can be way off in overcast or if shooting outside the ~10am-3pm window. HIE could give lots of 'effect' outside that window, but... alas it is no more. If you want screaming IR Wood effect, the best time to get it is in April or so (northern hemisphere) when the foliage is fresh green. On a sunny 16 day, high noon, in April, with a clear sky, my comp factor with the #87 goes down to ~10 stops. But I bracket. And when I say bracket, I don't mean +10,+11,+12, no sir! I mean bracket
liberally: +10, +12, +14. Then you'll get something useful for sure. Actually, I don't think I've ever overexposed a shot on the Rollei IR with the #87.... it's really hard to do!
By the way I also get good 'effect' with the superpan, I think I put something in the gallery earlier in the year which was done with superpan and an rm72 hoya filter, which may be like your 89b. The factors I used were much smaller, more like what was earlier mentioned- +5 or 6 or 7 or so. Same factor with the rollei IR. But do bracket!
Nope, the 87 isn't the same as the 89b, the 87 has a much deeper cutoff, hence the big factor. I think the 89b is more like the 72 hoya. There should be some curves somewhere online....