Hi. Firstly I would like to share the security issue about a web based Stokvel system. Here in South Africa this is taken as illegal to operate such system as much as people are offering donations at their own choices but since the government doesn't benefit from this, they then hunt the owners down.
The web system is not safe to operate this kind of business, and the main reason is that you do not host files but you register for an account with another company and if they find out the host company they demand it to shutdown you domain. Your site uses domain which can be resolved to IP address and locate your hosting company. The best way I've proven is run this as a software. Why? because: With software you host the server side at your computer and set proxy server so that it will point your location to another country. Its 100% reliable, safe, secure. Your clients can login and even send messages privately.
This is what I've been doing and its the best as IP address are hard coded and there is no chance of database hacking as the database is not online but on a private, unrouted IP address which is an IP address that can't be used over internet/WAN. I can create for you the best secured system which also has better performance speed, this is because the app divide it into threads and for each thread its can handle its client asynchronous. Think about your security, think about your clients, and think about performance, think of the control over your system, think software.