Hi!
Two very lovely girls!
Here is our comprehensive bonding guide, which also deals with questions such a quarantine yes or no?, living alongside yes or no? etc. in the run up to a bonding. Please take the time to read it; you will find it very helpful for the next few weeks as it covers the whole periodfrom the run up, the different phases of a bonding, sow bonding particulars and the post-bonding dominance phase which generally lasts around 2 weeks. It looks at typical behaviours and dynamics and also tells you what to expect if a bonding fails at any of these stages.
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
These are decisions that you have to make for yourself by weighing up the pros and cons for your individual situation. There is no one answer that fits all. Generally I find that a bonding is going more smoothly and with less fear agression if the newbie has had time to settle into their new home and make friends through the bars but this is not ideal wit babies or piggies that don't handle well being on their own.
Preparations also include having a plan B in case the girls don't take to each other. 5 months of age is teenage (ca. 4-14 months). Mutual liking and character compatibility are very much down to the unique dynamics between individuals and can therefore never be predicted - and sows can be so much more fickle to bond than boars, as every long term sow owner or rescue person running a dating service can tell you.!