I don't think that any of the skinny handguards support batteries there is literally no space between them and the outer barrel. It's not a show piece though because you can sell it with some loss obviously. Lots of people are into RS stuff here and it's a drop-in in most cases regarding gbb mp5's.
I bought a cheap clone of that particular handguard and had the same issues. Your best bet is the genuine magpul handguard or if you feel adventurous you could try something like this:
https://www.sixmm.com/en-gb/products/army-force-mp-style-mp5-m-lok-handguard-for-tokyo-marui-mp5-ngrs-gbb-seriesblk.
LCT is extremely overpriced crap without mosfet and decent internals. Yes, externally might be superior to others but in 2025 that's simply not enough when a sub 200 pound specna knows pre-cocking and programmable by few trigger pulls.
I use GBBR on HPA. Best of both worlds for me coz it's cost efficient and temperature doesn't matter. It's not as fun as a vanilla gas gun because it donesn't lock back on empty and reloading is less tacticool but I don't care personally.
The other thing with gas guns that I'm not gonna spend another 500 pounds on 8 gas magazines each time I buy something it's ridiculous...
I had a Gen.5 for a few months or so and I sold it because it's just another glock at the end of day. I understand that when you crave it it seems way better then what it is but I think it's extremely overhyped/overrated. 🤷♂️
I think it's more about the paper work from the seller's side than anything else. I bought at least a few guns from HK and never had an issue like this.