Hey:
Yeah; for kicks I've put some 6L6's in my Stiletto....both BEFORE and AFTER the bias mod.
Use the regular min/max recommendations for 6L6 tubes as a basic guideline and it'll work out O.K.
I didn't leave 6L6's in the Stiletto....just testing and evaluating. But some Mesa 6L6 tubes measured in at about 40ma/mv before I did the mod. I like my 6L6's to measure in mid 30's to low 40's. Don't remember which color code they were (sorry).
In both pre-mod and post-mod tests I was using the 6L6's only in the inner pair...where they only came into the circuit on the 100 watt setting. I really got a Stiletto to have an EL34 based amp to play along with with my Lonestar and didn't want to totally go over to 6L6's.
I do think the mixed sound of the EL34 outer pair and the 6L6 inner pair gives a very strong and distinctive tone. It does sounds good. I just can't decide whether I really want to use it that way...but if you get the chance...try it out...you may find it to be perfect for you.
Cheers, Charles