Letterbox are not support for mania.
As DE-CADE said use LN consistently.
Remember if want ranked may need hit sound
Offset : 834
Just
suggestion~
Copy below and paste to timing setup panel
834,346.820809248555,4,2,0,22,1,0
834,-111.111111111111,4,2,0,22,0,0
24591,-200,4,2,0,22,0,0
25112,-105.263157894737,4,2,0,22,0,0
36903,-111.111111111111,4,2,0,22,0,0
42452,-105.263157894737,4,2,0,22,0,0
50776,-100,4,2,0,22,0,0
53550,-100,4,2,0,22,0,1
75747,-105.263157894737,4,2,0,22,0,0
82857,-200,4,2,0,22,0,0
83550,-100,4,2,0,22,0,0
105053,-222.222222222222,4,2,0,22,0,0
105573,-100,4,2,0,22,0,0
Hard 00:04:996 - add
00:07:424 (7424|3) - remove
00:09:158 - shall have LN for piano
00:10:545 -
https://osu.ppy.sh/ss/204042600:16:094 - shall be 3 note. Therefore 00:16:441 (16441|0) - shall be at 00:16:094
00:16:961 (16961|1,17308|3) - remove. It's not loud and only piano sound
00:20:083 (20083|5) - shall be 00:20:256 -
00:21:643 -
https://osu.ppy.sh/ss/2040423 ? (this i follow sound)
00:26:152 - why here 2 but here 3 with same sound ? Suggest change 3 note to 2 note because consistent 3 note is too hard. 00:25:805 here 3 note because got crash sound.
00:29:274 - 00:29:620 - shall have LN or 3 note. Many sound here
00:33:089 (33089|6) - move to 00:32:742 and 00:33:435 - add another same length LN
00:38:985 (38985|6,38985|4,39158|5,39158|3,39331|4,39331|6) and 00:40:719 (40719|4,41759|5,41759|3,41759|1) - too hard for hard diff
00:49:736 (49736|1,49909|1,50083|1,50256|1) - jack shall be remove cause no same sound
00:52:684 (52684|0,52684|4,52771|1) - remove
00:54:938 (54938|3) - remove
00:54:245 (54245|6,55112|0) -
http://osu.ppy.sh/ss/2040445 01:03:089 (63089|4,63262|5) - remove
01:03:262 & 01:03:435 - can use jack
01:03:956 & 01:04:129 - ^
01:16:441 - add
01:19:216 - add
01:46:181 -
http://osu.ppy.sh/ss/2040453 for ending. After 01:46:961 left blank