I have a 9'x10' spa with a spillover to my pool. We use an all weather cover in the winter to keep the spa covered (unused in winter). The cover is a solid 4" which includes 3 panels, two of which fold over (3 panel). It's very bulky and difficult for one person to handle on his/her own. Are there lighter covers made that I can use in the summer that are easy to take on/off? Would a solar cover work or would it not stay in place due to the spillover? Do I even need a cover in the summer? I was thinking something to help retain the heat when not in use?