hi i have always used a ten,with my reps montain jacksons and others too with nooooooo problems at all, i know that some people choose to use the 5 on chams but is down to the keeper i think,provide some shade and some basking areas so he/she can et out of the u.v if it wants and you should be fine, with regards to chams like the veilds ect i think a 10defo as they are naturaly from quite a sun rich country and love the sun, my veild had one and you should have seen his beautiful bright colours...noooo brown in sight just pale yellowas and greens lovely good luck..p.s where did you get your mesh screen viv from?? im intrestedf in getting a metle one!!