[opennms-install] Error 404 - Availability bar for custom service

[<gui...@cy...>]

Hello!

I am in the process of switching (potentially) from Nagios to OpenNMS 
for our monitoring service. I have deployed OpenNMS (Version 16.0.3-1) 
on a virtual CentOS7 server using the rpm installation method described 
in the wiki (http://www.opennms.org/wiki/Installation:Yum).

After fiddling around a little I added a test server (minecraft) using 
the Provisioning Requisitions part of OpenNMS and made sure that SNMP 
was working fine for the default checks (SNMP, SSH and the likes). Then, 
seeing that this was working, I looked around in the wiki to learn how 
to add some SNMP checks to my test server (CPU, disk usage, load, etc.) 
just like I am used to.

The solution I found (probably not the best, you tell me) is to modify a 
few config files and then add the custom service created this way to a 
node in the provisioning requisition. The downsides I found to this 
method so far are:
1) When I remove a service in the config file (poller-configuration.xml) 
it stays in the drop-down of the web interface, no matter how many times 
I reload the service or restart the server
2) Some "custom" services do not show an availability bar. Instead, a 
"404 not found" is raised on the page for the bar object. I have 
searched the wiki for a more in-depth comprehension of this phenomenon 
but I only gathered that this is managed by the ReST part of the product.

The configurations I have added in "poller-opennms/etc/configuration.xml":
(Near the other services):
<service name="/data" interval="300000" user-defined="false" status="on">
         <parameter key="oid" value=".1.3.6.1.4.1.2021.9.1.9.9"/>
         <parameter key="operator" value="&lt;"/>
         <parameter key="operand" value="85"/>
</service>
(By the end of the file):
<monitor service="/data" 
class-name="org.opennms.netmgt.poller.monitors.SnmpMonitor" />

My questions are as follows:
-Is there a better way to add a check on other SNMP things from a 
server? I tried a solution before named NetXMS and I was able to 
communicate with the Nagios plugin already installed on all my servers.
-If there is a better solution, where can I read some documentation 
about it?
-Why is the Availability Bar "not found"?

Thanks for any feedback/questions/input/comments/interactions!

-*Guillaume Ross***