I boosted the chems a bit...I think I should be around 1:15 then did the tray trick you had in mind with a 20x24 tray and put my 11x14 in it with boiling hot water. Helped, but still took up to 15 minutes. I'll try to get some scans soon. This time was VERY grainy. Almost too much so. Might need to make some adjustments.
Not very experienced in lith, just used LD20 in regular dilution (+ "old brown"); also tried Fomabrom Variant and got 20 minutes developing time at 20°C and very, very grainy. 20 minutes just too much!
Got the advice her on APUG to heat up. I changed paper to Fomabrom 131 and at 25°C I got nice developing time like 2-4 minutes and, at least, sometime interesting results (some posted at the Standard Gallery). Have just ordered some Fomabrom 111 graded paper, grade Normal, which they say is nice for lith, haven't tried it yet.