[ifazeiux] Some long chess endgames

All positions (given in FEN notation) white to move.

KRRPKQ mate in 253 moves. Promote the c2 pawn (sacrificing one rook), converting to KQRKQ.
q7/7k/8/6R1/8/8/2P2R2/K7 w - - 0 1

KQRKQ mate in 67
8/8/8/8/q7/6k1/8/KR5Q w - - 0 1

KRPKR mate in 74. Advance the g2 pawn. Converts to KRK (maybe others which convert to KQKR)
k7/8/8/8/8/4R3/6P1/1K5r w - - 0 1

KQPPKQ mate in 182. Promote the a2 or h3 pawns. Eventually becomes KQPKQ.
8/4k3/8/Q7/8/7P/P7/q1K5 w - - 0 1

KPPKP mate 127. White has doubled pawns e3 and e4; black has b4 pawn. Quickly becomes KQPKQ.
8/8/8/8/1p2P3/4P3/1k6/3K4 w - - 0 1

KQPKQ mate in 124. Promote the e2 pawn.
4Q3/8/7q/8/8/8/k3P3/2K5 w - - 0 1

KQKRP mate in 104. Capture black f3 pawn, converting to KQKR.
8/Q7/K7/5r2/5p2/8/6k1/8 w - - 0 1

KQPKQP mate in 151. White h6 pawn versus black c6 pawn. Converts to KQPKQ.
8/3q4/2p4P/8/7Q/1k6/8/K7 w - - 0 1

KPPKPP mate in 141. White pawns f5, h6; Black c3, e6. Quickly converts to KQPKQP with h6 and c3 pawns.
8/8/2p4P/5P2/1k6/4p3/K7/8 w - - 0 1

KQRKQR mate in 117. Converts to KQKR.
4q3/7R/8/4r2Q/8/4k3/8/2K5 w - - 0 1

KBBPKR mate in 180. Advance the g2 pawn.
2B5/4Br2/K1k5/8/8/8/6P1/8 w - - 0 1

KQKBB mate in 81
8/1Q6/8/8/2bb4/8/3k4/K7 w - - 0 1

KQKNN mate in 72
8/8/8/8/4n2Q/3k4/8/3K3n w - - 0 1

KQKRN mate in 69. Converts to KQKR.
8/5Q2/8/n7/8/4k3/8/3K2r1 w - - 0 1

KBBKNP mate in 131. Capture the black b4 pawn and convert to KBBKN
K7/8/8/k7/Bp6/7n/7B/8 w - - 0 1

Some classic ones:

KQKR mate in 35
8/8/8/8/2r5/8/2k5/K6Q w - - 0 1

KNNKP mate in 115. The extra pawn prevents stalemate. Would be nice to have longest checkmates for each file the pawn can be in. (Troitzky line)
1N6/8/p7/8/8/8/2k1N3/K7 w - - 0 1

KRBKR mate in 65. (Cochrane)
8/3B4/8/1R6/5r2/8/3K4/5k2 w - - 0 1

KBBKN mate in 78. (Kling Horwitz)
7B/6n1/8/6k1/6B1/8/8/K7 w - - 0 1

Some (supposedly) elementary:

KBNK mate in 33
8/8/7N/8/8/8/8/K1k1B3 w - - 0 1

KRKP mate in 26. Black pawn on d5.
8/8/K7/3p4/8/3k4/4R3/8 w - - 0 1

KRKN mate in 40
8/2R5/8/8/7k/3K4/8/4n3 w - - 0 1

KRKB mate in 29
8/8/8/8/8/2R5/8/3K1bk1 w - - 0 1

KQKP mate in 28. Black pawn on d2.
3Q4/3K4/8/8/8/3k4/3p4/8 w - - 0 1

KQKN mate in 21
8/8/8/8/8/2k5/2n5/KQ6 w - - 0 1

KQKB mate in 17
8/6Q1/8/4b3/3k4/8/8/K7 w - - 0 1

KQKQ mate in 13
8/8/8/8/8/8/8/qk1K2Q1 w - - 0 1

Some monsters:

KRNKNN mate in 262. Discovered by Stiller, also with KRBKNN (mate in 238).
6k1/5n2/8/8/8/5n2/1RK5/1N6 w - - 0 1
8/8/8/8/2n2k2/2n5/5BR1/1K6 w - - 0 1

KQNKRBN convert in 517. Bourzutschky and Konoval.
8/1r6/8/6n1/5k2/1b6/3K3N/7Q w - - 0 1

KQPKRBN mate in 549. Lomonosov tablebase.
1n1k4/6Q1/5KP1/8/7b/1r6/8/8 w - - 0 1

All but the last two positions were selected from Kryukov's longest checkmates page based on 6-man Nalimov tablebases. Some flaws: KRNKBB has same-colored bishops. Lots of underpromotions, e.g., KRPKBB, KBBKP and KBBKPP to knight, KRPPKQ to rook. KNNKPP is empty. Positions maximizing distance to conversion would be nice, especially for currently quick conversions like KPPKPP.

What happens if these endgames are played on larger boards? The 4-piece ones may be doable.