I have configured my solrconfig.xml and schema.xml to query for the suggestions.
I am able to get the suggestions from the url
http://localhost:8080/
Passing the qt parameter does NOT work, at least not in Solr 4.7 even with handleSelect=true in SolrConfig. You can verify by specifying a custom handler that's very dissimilar from the default /select, say make yours use edismax and send debugQuery = true in ExtraParams and catch the results in Fiddler.
Also if you read the explanation on the handleSelect flag it says "if the request uses "/select" but there is no request handler by that name".
You don't want to touch or disable the /select handler because Solr uses it itself.
I ended up using ExtraParams to pass all the values I defined in my custom handler, there weren't that many. Seemed better than just using part of SolrNET and then doing the result parsing.