man i thought holds were gonna be a bitch to install...if you get the right directions its actually quite easy...the hardest part is the turf, which, if you get a kit is not that bad.
i have no experience with mashers, but my buddy had lifters which fell off after 3 sessions.
Maybe with the mashers, you could strip down the tray, attach the mashers, then turf over it? maybe it would hold them in better im not sure.
would hate to see you spend your cash on something thats gonna provide you with subpar results.