We have studied the Wireless Internet-access Mesh NETwork (WIMNET) as a large-scale multihop wireless network using Wireless Distribution System (WDS) for Internet access network. We have proposed the heuristic algorithm for the WDS clustering problem to achieve the scalable WIMNET. In this paper, we propose the four improvements of our algorithm; 1) consideration of total hop counts and total interferences in the cost function, 2) random selection of starting APs, 3) modification of the cost function for the gateway AP selection, and 4) consideration of interferences for the route selection. Through simulations using two types of network topologies, we verify the effectiveness of these improvements.