Apologies I hadn’t realised the hole option from Warbases was for larger sizes. It would be possible to hand drill the holes (maybe make a jig) but this may drive you to madness depending upon how many chaps you’re doing. It might be possible to have the minihammer bases made with 1/2mm holes as a custom order as this size would be perfect for most 10mm.
The best advice I can give is to contact Warbases (if you’re U.K. or in a place UK friendly postage wise) and ask them as they are very helpful, talented and reasonably priced requiring low minimum orders (for my custom orders). They are great people and I can’t recommend them enough. If I had more money I’d be constantly emailing them with random, niche ideas.
We (my favourite opponent and I) originally based our minis directly onto thin self adhesive 10mmx10mm magnets (bought in sheets) these might be a possible addition to the mdf bases - just have to watch the overall thickness so you don’t lift the minis up too much (although this is just my aesthetic opinion and thus not necessarily important to you).
I haven’t added anything with my original pieces as they’re mainly metal warmaster cut/re sculpted on individual bases in a specific unit tray base so they’re quite heavy, fit tightly together and are pretty secure when in their base (and I haven’t taken them anywhere). My newer pieces are 3D printed and super light (and at times explosively fragile) and will probably need the additional security magnets would add. This is something I’m currently looking at so I’ll see if I can locate the other older half of my project.
Balm