The first thing to consider is where you're going to do the installation. If the outside temperature is higher than 75 F the installation should be done out of the direct sun light. The adhesive on the Velcro requires 24 hours to take full bond and during that period extremely high or low temperatures should be avoided. Next we want to make sure the areas where the Velcro strips are going to be placed are clean and dry. The best way to do that is with a clean rag and a 50:50 mixture of isopropyl (rubbing) alcohol and water (do not use other cleaners: Windex, 409, ArmorAll... they leave a residue). Now you're ready to install your headliners. The adhesive should be applied at room temperature, with the ideal room temperatures being 65°F to 75°F, and relative humidity 40% to 65%. (The lower the humidity, the better the bond.) Excessive cold, heat, dirt and relative humidity will be detrimental to your adhesive performance. If adhesive must be applied at temperatures lower than 65°F, warm your hard top and the Velcro to an elevate temperature prior to applying. This can be done with a blow drier, electric heater, or running the heater in your Jeep. That will help the adhesive cure. With an outside temperature of 80°F the surface temperature of your black hard top is about 160°F when sitting in the sun.
For maximum bond strength the surfaces need to be clean and dry. Thorough cleaning is best achieved with a 50:50 mixture of isopropyl (rubbing) alcohol and water (do not use other cleaners: Windex, 409, ArmorAll... they leave a residue). Ideal tape application is accomplished when temperature is between 70°F and 100°F (21°C and 38°C). Initial tape application to surfaces at temperatures below 50°F (10°C) is not recommended. Bond strength is dependent upon the amount of adhesive-to-surface contact developed. Firm application pressure develops better adhesive contact and helps improve bond strength. 15 pounds of direct pressure is what is recommended by 3M. Please us the square of cardboard provided to push up on your headliner panels because using just your hand may leave an impression in the headliner fabric.
Bond strength increases with time. If applied at 65- 70°F approximately 50% of the ultimate bond strength is achieved after 20 minutes, 90% after 24 hours, and 100% after 72 hours. Higher temperatures achieve ultimate bond strength quicker, so if it's 110°F outside it's okay to install your headliners. Just do so in the shade. It's not recommended put your Jeep in direct sunlight for at least 12 hours after installation if it's hotter than 85°F outside. With an outside temperature of 80°F the surface temperature of your black hard top is about 160°F when sitting in the sun.
Removing your Velcro headliners: Start in a corner were you can get a finger in under the panel. You can also carfully use a flat screw driver or putty knife to get a corner down enough to get your fingers in. Gently pull down with one hand while sliding the other hand up under the panel. What you want to do is slide one hand between the two sides of the Velcro to separate them. Just start at one side of the panel and work your way across in this way until all the Velcro is separated. You'll find that the panels will come down quite easily like this, but to just try to grab a corner and pull them down is almost impossible.