Some solar scopes have an etalon which is always perpendicular to incoming light, with tuning accomplished by changing air pressure (lunt pressure tune) or mechanically compressing the etalon (PST). These scopes can be double stacked without returning to the factory; because the double stack etalon has some tilt (compared to zero tilt of the first etalon) there's no risk of ghost images.
Other solar scopes (including the Solarmax II 60) tune the internal etalon via mechanical tilting and it's safer to have the scope double stacked at the factory to avoid the possibility of getting ghost images if both etalons come on band at the same degree of tilt.
Even without the ghost image problem you can get varying performance (good or great) depending on how well matched the etalons are.
You could ask Bintel if they would allow you to try a new double stack etalon at the shop and buy it if there are no ghost images - far better option than the expense and risk of shipping the scope to Meade. Failing that you could ask to buy a double stack etalon which comes on band (tunes) with a large amount of tilt which should minimze your risk of ghost images - theoretically the single etalon scope should be built with an etalon that tunes with minimal tilt as it is preferable to have the double stack etalon tune with more tilt than the first etalon. (lots of etalons there
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