F D B L U' // eo, dr-4c4e 5/5
B D2 B2 R2 B R // dr (2c3 4e) 6/11
U2 B' R2 D2 R2 L2 [B' L2 B' // htr 9/20
F2] L2 U2 L2 U2 // leave slice 5/25
Sliceable dr solution but no -1. [] = F B2 U2 F
DR opt +1. I didn't realize you could insert U2 in the U R2 * S2 U trigger for +1 extension, which would have yielded optimal. Now I know!

F' L D R // eo, dr-7c8e 4/4
(R2 L2 D B U) // dr (4b2 6e) 5/9
// This dr saved the attempt fr
(L2 D2 F2 U2 F' L2 B) // htr 7/16
(D2 [1] L2 B2 D2 [2] B2) // leave wrong slice 5/21
[1] = E'. [2] = E // solved in 23
Of course mallard finds bs 19 from a longer dr off same rzp.
Missed dr opt by 1, needed 4q though so I'm ok with that. Also found 21 to slice off this dr but it was +2 opt rip.