Silencing the UE Super.Fi 5 Pro EB

[vilms5000]

Hello all... just after some suggestions to fix what I think has been an expensive mistake!

I've been using Etymotic phones for years, but found them to be so fragile for everyday use (especially running), that I bought the UEs on the basis of their rugged construction - hopefully avoiding the need to resolder new 3.5mm jacks on every so often. However, I'm finding the bigger earphone to be painful to use (I mean, it's physically bigger, so I know this will take some getting used to) for extended periods, but the killer for me is how much sound they bleed.

Part of the attraction of these types of 'phones is their isolation from the surrounding environment. The flipside is that I expect them not to bother anyone else!

The UEs appear to be ported. Is it as simple as blocking these up? What material would work best? I'm thinking blu-tack!

TIA Paul