Changing from #S1P with larger capacity cells is usually "safe enough" [tm].
Using recovered cells also probably safe enough [tm][again] BUT see notes below.
As Ignacio said, the cells which show around 4V are probably OK - but they will have lower capacity than new.
Note - LiIon / LiPo charging:
Normal LiIon / LiPo charge mode is to charge in CC (Constant Current) mode at Imax of typically say C* (C = current in mA numerically equally to battery capacity in mAh) until Vmax is reached then in CV (Constant Voltage) mode until I drops to X% of Imax.
- X% may be 50% to 5% with smaller percentages resulting in higher max stored capacity - but low X% is hard on battery life and does not gain much capacity.
Stopping charging at 25% of Imax or even 50% is probably a reasonable choice.
0% and 5% is for 'road warriors' who do not pay for their replacement batteries.
[*Imax in terms of C is usually set by battery manufacturer. Normal is Imax = C.
Some few have Imax = C/2 and a few have Imax = 2C.
Special cells with Imax >>C exist but are not usually found in consumer equipment.
When charging xS1P stack with a 2 wire connection, if the cells are of differing capacity (due to cycles of use) they will reach the CC/CV changeover knee at different times in the charging cycle.
eg in a 3S1P pack one cell may be at 4.2V (should be in CV mode) and two at say 4.0V. The charger sees 12.2V total, is waiting for a 3 x 4.2 = 12.6V pack voltage before changing to CV mode, SO keeps charging at CC when one cell is already at Vmax. This will potentially drive the cell above 4.2V until the three cells combine to provide 12.6V total. As the cell that is being overdriven is the one that probably has least capacity (as it reached the Vmax limit first when charged the same as the other cells) this arrangement is most liable to damage the already most damaged cell. :-(. As the cells are from a low cost or free source this is liable top be acceptable from a lifetime achievable perspective but increases the "halt and catch fire" / vent with flames possibility. As you are charging at lower C rating (1300 mA charger with nominally 2200 mAh cells = 1300/2200 = 0.59C = C/1.7, you are probably "safe enough" [tm].
Changing from XX1P to XX2P often works OK but introduces a greater chance of cell imbalance if you charge the pack as a whole (which you would probably do with a simple charger). The low I charger will charge the high capacity OK but slower - but better than N times slower as charging at < Imax increases charge% at which Vmax is reached.
However if the charger is set to terminate at say 10% of 1300 mA = 130 mA this will now be 130/2200 ~+ 6% of 2200 mA and ~-3% of 4400 mA. SO using a small current charger with high capacity battery packs will give a slow charge BUT a higher charge % than originally.
If you care (!!!) then checking individual cells occasionally to see if some are reaching 4.2V first MAY help lifetimes if you are willing to boost them with an isolated charger.
The "ideal" arrangement is N floating chargers for N cells with taps to all cells and a multi way plug. This is functionally what top equipment actually does.
If one cared this could be done with relative ease. For a 6 cell pack 6 floating 2A wall wart LiIon chargers connected one per cell would do an excellent job.