Some open source real world figures.
12(B) Sqn, Lossiemouth, maritime role with Sea Eagle on GR1(B) until the 90s.
4x1500l tanks used operationally by GR1(A)s in Gulf 1 on a regular basis. Internal recce kit hence no need for under fuselage weapons.
2x2250l inboard wings and 2x1500l underfuselage flown occasionally to ferry the GR4. That just gives Lajes - St Johns if headwind < 100kts. Take-off from Lajes is balanced with the cable, but it is a pig to fly!!
2x2250l is less drag than 3x1500 for the same fuel load, but the g limit with full 2250s is quite restrictive hence Sqns often use 3x1500l and a CBLS if they want more fuel and a respectable ish g limit.
Hope that helps.
Fin