lith film for enlarged negs

An old chestnut I know but I'm not getting the results I need. Film is Agfa CE cut from 60m rolls and I'm contact printing RC prints to get the enlarged neg. Here's the story.

I'm enlarging 4x5 to 24x30 to make gum prints - density range not critical but 1.0 to 1.4 is ideal. My exposure time I find is independent of the lith film developer I try - 30s at f22 with 1s pre-flash at f45 (for comparison my normal silver gelatin enlarging time with the same geometry is 30s at f32).

For developer I've tried the ususal suspects - Soemarko LC1, dilute D23, POTA, dilute pyrocat etc. I find I get the best range and separation of tones with D163 1:10 and 1min with continuous agitation - something which everone tells me should not be optimal. Agreed the curve isn't great - bottom and top end are both compressed and mid range expanded, but its the best I've got so far.

So why does an inappropriate devloper work best? How can I expand top and bottom ends and compress the middle? Thoughts welcome

I'd try this: http://www.ultrafineonline.com/ulcotodufi20.html

Thanks - thats worth knowing. I'll check if they can do the size I need.

I don't understand your problem with LC-1 or D-23. I use these very successfully. I do not dilute the D-23, but use divided D-23, 3 minutes in "A" and 3-5 Minutes in "B".
I only use D-23 when I am too lazy to mix Soemarko formula. I also have success with HC 110 diluted 1+15 to 1+20 from stock.

Be very careful of agitation - it needs to be very gentle.