On my Challenges I used the old maxim of “plan for the worst and hope for the best”. Everyone has different comfort/weight trade offs. The things I considered were:
1. how would I manage several cold, wet days in a row?
2. how would I manage hot sunny days (don’t forget sun screen and a hat!)?
3. how would I manage river crossings (footwear, trekking poles)?
4. would my tent stand up to high winds/rain (I used a Scarp 1 on three Challenges and a Tramplite on one)?
5. I took an extra set of clothes for hotels and so I could wash my clothes in civilisation.
6. did I have enough pairs of socks to rotate and wash?
7. it’s a holiday!
You will probably have different trade offs to me, but that’s your decision. I used a Mariposa on all my Challenges and found it ideal. If you are restocking with food from small supermarkets you often end up with more bulk than normal so having a bit of spare capacity can be useful.