Tuning oldschool bombers

[Rik]

As you don't know, I'm running a 1998 Mr T fork, with dual dampers.
It's a nice fork, but right now, even with the extra stiff springs and high level of 10wt oil, I'm bottoming them out a bit more than I'd like.
I'm about to change what bike they're on, and want something fairly slow.
Will jumping to 15wt oil cause any hassles? I'll buy new seals when I do it, but has anyone had experiences with this vintage fork and tuning it to take big hits?

Ideally, I'd like it to ride similar to a DJ, for big hits only, as it's going on a street-orientated bike. Are there any other suggestions to tune it up to take the big stuff?
Any worthwhile information will be appreciated.

 

[j5ive]

You might have to get some springs made. Going to 15 weight is really going to slow them down but have minimal effect on bottoming performace.

 

[CHEWY]

tried increasing the oil height?
EDIT: Re-reading your post you obviously have. Is it up to the max height yet?

 

[Rik]

I kept on increasing it gradually... until I blew a seal

I plan to rebuild them sometime soon, new seals, and 12.5wt oil. I guess I may just have to fark about for a bit until I can find what works best. I've been told going to 15wt might not be the best solution either... only one way to find out though.