Welcome to the forum.
Regarding the elastic,
Is it a solid elastic, hollow elastic, or what they call a hybrid elastic.?
Plus it will also depend how tight you have it set and if using side pullers, bottom puller or just standard bung.
I have a mix of solid and hollow elastics,
Your 10/12 should handle Tench , bream, large F1, and lower figure carp around 8lb.
I wouldn't use it for margin work.
I have had carp to 15lb on a 14/16 Preston slip solid, and also Preston 15h hollo.
It was easier to play them on the solid elastic than the hollo due to the difference in stretch. Both topkits had side pullers.
How many sections of topkit are you running it through ,?
Edit,.... just noticed it is a hollow elastic, 2.3mm dia.
I would say fine for open water, but not margin or snag work.
I would use it with a puller system, that way you have greater control when playing the larger fish.
Also at nearly £18 a packet I would also be looking at the Diawa Hybrid elastic and either Preston dura hollo or Preston Hybrid.
Personally I would steer clear of Drennan bungee. I had 16/18 in a margin pole, I got seen off to many times using it, both down the side and open water.
The 6/8 bungee is a decent open water elastic compared to the higher numbers.
These are just my opinions based on what I use, others on here will have their own views.Also I have no affiliation to any of the brands mentioned.