In another thread Don Pensack recommends 20 10 and 7 with a 2x Barlow. I'd add a 28mm to that for a sub f5 dob.
Get a 2" barlow for wide field 28mm eyepieces are 2" barrels.The 28 becomes a 14mm which is perfect in-between the 20mm and 10mm.
Has taken me years to work out what I like and what goes best with which scope. Still making mistakes
Matt