Yeah I think for it to work properly you'll have to change your subnet. Maybe not, so give it a go. But what happens is when he connects he gets routing information telling him that anything on the 192.168.0.0/24 subnet is now on the vpn gateway, so he may not be able to access his network properly. But openvpn might have some built in witchcraft that sorts it out.
No worries, you might want to have a look at this one too if you haven't already: https://teksyndicate.com/forum/networking-hardware/vlan-help/181819
Just to let everyone know, in case I didn't list it already down here somewhere, the bottleneck here was my access point. I was using a wireless G access point and a gigabit switch and network. Just the wireless clients ground to a halt, which included my laptop, so that was confusing. I bought an Ubiquiti N AP several months ago and haven't had to implement any kind of traffic shaping since, even when transferring several gigabytes of files at a time, watching YouTube, and reading stuff simultaneously. WiFi really is a pain sometimes :P