Take an 8th note triplet and add a sextuplet double on the first note, for a total of four notes.
R-L-R turns into RR-L-R, keeping the triplet feel.
I believe this is correct for 16th notes, but I could have the name wrong...someone please correct me if I'm wrong.
Put 32nd note doubles, or singles if you wish, on the first two notes of a group of 16th notes.
R-L-R-L turns into RR-LL-R-L.
And, of course, you can move those all around within each grouping. R-LL-R, R-LL-RR-L, etc..